     [file common.texi not included]

This document is an unofficial reference manual for LaTeX, a document preparation system, version of October 2018.

This manual was originally translated from LATEX.HLP v1.0a in the VMS Help Library.  The pre-translation version was written by George D. Greenwade of Sam Houston State University.  The LaTeX 2.09 version was written by Stephen Gilmore.  The LaTeX2e version was adapted from this by Torsten Martinsen.  Karl Berry made further updates and additions, and gratefully acknowledges using Hypertext Help with LaTeX, by Sheldon Green, and LaTeX Command Summary (for LaTeX 2.09) by L. Botway and C. Biemesderfer (published by the TeX Users Group as TeXniques number 10), as reference material.  We also gratefully acknowledge additional material appearing in latex2e-reference by Martin Herbert Dietze.  (From these references no text was directly copied.)

Copyright 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018 Karl Berry.

Copyright 1988, 1994, 2007 Stephen Gilmore.

Copyright 1994, 1995, 1996 Torsten Martinsen.

Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.

Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions.

LaTeX2e: An unofficial reference manual
***************************************

This document is an unofficial reference manual (version of October 2018) for LaTeX2e, a document preparation system.

About this document
*******************

This is an unofficial reference manual for the LaTeX2e document preparation system, which is a macro package for the TeX typesetting program (see Overview).

This document's home page is LTXREFMAN_HOME_PAGE.  There you can get the sources, subscribe to the mailing list or read its archives, see other infrastructure, and get the current output in various formats.  In particular, the output comes in two web formats. Probably the most convenient one, shown at http://latexref.xyz/, has pages for each topic and so is good for a quick lookup; see also the note there about easy-to-remember links.  The other, shown at http://svn.gnu.org.ua/viewvc/latexrefman/trunk/latex2e.html?view=co, has all the information on single page.

In this document, we will mostly just use `LaTeX' rather than `LaTeX2e', since the previous version of LaTeX (2.09) was frozen decades ago.

LaTeX is currently maintained by a group of volunteers (http://latex-project.org).  The official documentation written by the LaTeX project is available from their web site.  This document is completely unofficial and has not been reviewed by the LaTeX maintainers. Do not send bug reports or anything else about this document to them. Instead, please send all comments to LTXREFMAN_BUGS.

This document is a reference.  There is a vast array of other sources of information about LaTeX, at all levels.  Here are a few introductions.

http://ctan.org/pkg/latex-doc-ptr
     Two pages of recommended references to LaTeX documentation.

http://ctan.org/pkg/first-latex-doc
     Writing your first document, with a bit of both text and math.

http://ctan.org/pkg/usrguide
     The guide for document authors that is maintained as part of LaTeX. Many other guides by many other people are also available, independent of LaTeX itself; one such is the next item:

http://ctan.org/pkg/lshort
     A short introduction to LaTeX, translated to many languages.

http://tug.org/begin.html
     Introduction to the TeX system, including LaTeX, with further references.

Overview of LaTeX
*****************

LaTeX is a system for typesetting documents.  It was originally created by Leslie Lamport and is now maintained by a group of volunteers (http://latex-project.org).  It is widely used, particularly for complex and technical documents, such as those involving mathematics.

A LaTeX user writes an input file containing text along with interspersed commands, for instance commands describing how the text should be formatted.  It is implemented as a set of related commands that interface with Donald E. Knuth's TeX typesetting program (the technical term is that LaTeX is a macro package for the TeX engine).  The user produces the output document by giving that input file to the TeX engine.

The term LaTeX is also sometimes used to mean the language in which the document is marked up, that is, to mean the set of commands available to a LaTeX user.

The name LaTeX is short for ``Lamport TeX''.  It is pronounced LAH-teck or LAY-teck, or sometimes LAY-tecks.  Inside a document, produce the logo with \LaTeX.  Where use of the logo is not sensible, such as in plain text, write it as LaTeX.

Starting and ending
===================

old name

LaTeX files have a simple global structure, with a standard beginning and ending.  This is a small example.

     \documentclass{article}
     \begin{document}
     Hello, \LaTeX\ world.
     \end{document}

Every LaTeX document has a \begin{document} line and an \end{document} line.

Here, the article is the document class.  It is implemented in a file article.cls.  You can use any document class on your system.  A few document classes are defined by LaTeX itself, and vast array of others are widely available.  See Document classes.

You can include other LaTeX commands between the \documentclass and the \begin{document} commands. This area is called the preamble.

The \begin{document}, \end{document} pair defines an environment; the document environment (and no others) is required in all LaTeX documents (see document).  LaTeX make available to you many environments that are documented here (see Environments).  Many more are available to you from external packages, most importantly those available at CTAN (see CTAN).

The following sections discuss how to produce PDF or other output from a LaTeX input file.

Output files
============

LaTeX produces a main output file and at least two auxiliary files. The main output file's name ends in either .dvi or .pdf.

.dvi
     If LaTeX is invoked with the system command latex then it produces a DeVice Independent file, with extension .dvi.  You can view this file with a command such as xdvi, or convert it to a PostScript .ps file with dvips or to a Portable Document Format .pdf file with dvipdfmx. The contents of the file can be dumped in human-readable form with dvitype.  A vast array of other DVI utility programs are available (http://mirror.ctan.org/dviware).

.pdf
     If LaTeX is invoked via the system command pdflatex, among other commands (see TeX engines), then the main output is a Portable Document Format (PDF) file.  Typically this is a self-contained file, with all fonts and images included.

LaTeX also produces at least two additional files.

.log
     This transcript file contains summary information such as a list of loaded packages.  It also includes diagnostic messages and perhaps additional information for any errors.

.aux
     Auxiliary information is used by LaTeX for things such as cross references.  For example, the first time that LaTeX finds a forward reference---a cross reference to something that has not yet appeared in the source---it will appear in the output as a doubled question mark ??.  When the referred-to spot does eventually appear in the source then LaTeX writes its location information to this .aux file.  On the next invocation, LaTeX reads the location information from this file and uses it to resolve the reference, replacing the double question mark with the remembered location.

LaTeX may produce yet more files, characterized by the filename ending.  These include a .lof file that is used to make a list of figures, a .lot file used to make a list of tables, and a .toc file used to make a table of contents (see Table of contents etc.).  A particular class may create others; the list is open-ended.

TeX engines
===========

LaTeX is defined to be a set of commands that are run by a TeX implementation (see Overview).  This section gives a terse overview of the main programs (see also Command line).

latex
pdflatex
     In TeX Live (http://tug.org/texlive), if LaTeX is invoked via either the system command latex or pdflatex, then the pdfTeX engine is run (http://ctan.org/pkg/pdftex). When invoked as latex, the main output is a .dvi file; as pdflatex, the main output is a .pdf file.

     pdfTeX incorporates the e-TeX extensions to Knuth's original program (http://ctan.org/pkg/etex), including additional programming features and bi-directional typesetting, and has plenty of extensions of its own.  e-TeX is available on its own as the system command etex, but this is plain TeX (and produces .dvi).

     In other TeX distributions, latex may invoke e-TeX rather than pdfTeX.  In any case, the e-TeX extensions can be assumed to be available in LaTeX.

lualatex
     If LaTeX is invoked via the system command lualatex, the LuaTeX engine is run (http://ctan.org/pkg/luatex).  This program allows code written in the scripting language Lua (http://luatex.org) to interact with TeX's typesetting. LuaTeX handles UTF-8 Unicode input natively, can handle OpenType and TrueType fonts, and produces a .pdf file by default. There is also dvilualatex to produce a .dvi file, but this is rarely used.

xelatex
     If LaTeX is invoked with the system command xelatex, the XeTeX engine is run (http://tug.org/xetex).  Like LuaTeX, XeTeX natively supports UTF-8 Unicode and TrueType and OpenType fonts, though the implementation is completely different, mainly using external libraries instead of internal code.  XeTeX produces a .pdf file as output; it does not support DVI output.

     Internally, XeTeX creates an .xdv file, a variant of DVI, and translates that to PDF using the (x)dvipdfmx program, but this process is automatic.  The .xdv file is only useful for debugging.

Other variants of LaTeX and TeX exist, e.g., to provide additional support for Japanese and other languages ([u]pTeX, http://ctan.org/pkg/ptex, http://ctan.org/pkg/uptex).

LaTeX command syntax
====================

In the LaTeX input file, a command name starts with a backslash character, \.  The name itself then consists of either (a) a string of letters or (b) a single non-letter.

LaTeX commands names are case sensitive so that \pagebreak differs from \Pagebreak (the latter is not a standard command). Most commands are lowercase, but in any event you must enter all commands in the same case as they are defined.

A command may be followed by zero, one, or more arguments. These arguments may be either required or optional.  Required arguments are contained in curly braces, {...}.  Optional arguments are contained in square brackets, [...].  Generally, but not universally, if the command accepts an optional argument, it comes first, before any required arguments.

Inside of an optional argument, to use the character close square bracket (]) hide it inside curly braces, as in \item[closing bracket {]}].  Similarly, if an optional argument comes last, with no required argument after it, then to make the first character of the following text be an open square bracket, hide it inside curly braces.

Some of LaTeX's commands are a declaration.  Such a command changes the value the meaning of some other command or parameter.  For instance, the \mainmatter declaration changes the typesetting of page numbers from roman numerals to arabic (see \frontmatter & \mainmatter & \backmatter).

LaTeX has the convention that some commands have a * form that is related to the form without a *, such as \chapter and \chapter*.  The exact difference in behavior varies from command to command.

This manual describes all accepted options and *-forms for the commands it covers (barring unintentional omissions, a.k.a. bugs).

Environment
===========

Synopsis:

     \begin{ENVIRONMENT NAME}
       ...
     \end{ENVIRONMENT NAME}

An area of LaTeX source, inside of which there is a distinct behavior.  For instance, for poetry in LaTeX put the lines between \begin{verse} and \end{verse}.

     \begin{verse}
       There once was a man from Nantucket \\
       ...
     \end{verse}

See Environments for a list of environments.  Particularly notable is that every LaTeX document must have a document environment, a \begin{document} ... \end{document} pair.

The ENVIRONMENT NAME at the beginning must exactly match that at the end.  This includes the case where ENVIRONMENT NAME ends in a star (*); both the \begin and \end texts must include the star.

Environments may have arguments, including optional arguments.  This example produces a table.  The first argument is optional (and causes the table to be aligned on its top row) while the second argument is required (it specifies the formatting of columns).

     \begin{tabular}[t]{r|l}
       ... rows of table ...
     \end{tabular}

CTAN: the Comprehensive TeX Archive Network
===========================================

The Comprehensive TeX Archive Network, CTAN, is the TeX and LaTeX community's repository of free material.  It is a set of Internet sites around the world that offer material related to LaTeX for download.  Visit CTAN on the web at https://ctan.org.

This material is organized into packages, discrete bundles that typically offer some coherent functionality and are maintained by one person or a small number of people.  For instance, many publishers have a package that allows authors to format papers to that publisher's specifications.

In addition to the massive holdings, the web site offers features such as search by name or by functionality.

CTAN is not a single site, but instead is a set of sites. One of the sites is the core. This site actively manages the material, for instance, by accepting uploads of new or updated packages. It is hosted by the German TeX group DANTE e.V. Other sites around the world help out by mirroring, that is, automatically syncing their collections with the core site and then in turn making their copies publicly available. This gives users close to their location better access and relieves the load on the core site. The list of mirrors is at https://ctan.org/mirrors.

Document classes
****************

The document's overall class is defined with this command, which is normally the first command in a LaTeX source file.

     \documentclass[OPTIONS]{CLASS}

The following document CLASS names are built into LaTeX. (Many other document classes are available as separate packages; see Overview.)

article
     For a journal article, a presentation, and miscellaneous general use.

book
     Full-length books, including chapters and possibly including front matter, such as a preface, and back matter, such as an appendix (see Front/back matter).

letter
     Mail, optionally including mailing labels (see Letters).

report
     For documents of length between an article and a book, such as technical reports or theses, which may contain several chapters.

slides
     For slide presentations---rarely used today.  In its place the beamer package is perhaps the most prevalent (see beamer template).

Standard OPTIONS are described in the next section.

Document class options
======================

You can specify global options or class options to the \documentclass command by enclosing them in square brackets.  To specify more than one OPTION, separate them with a comma.

     \documentclass[OPTION1,OPTION2,...]{CLASS}

Here is the list of the standard class options.

All of the standard classes except slides accept the following options for selecting the typeface size (default is 10pt):

     10pt  11pt  12pt

All of the standard classes accept these options for selecting the paper size (these show height by width):

a4paper
     210 by 297mm (about 8.25 by 11.75 inches)

a5paper
     148 by 210mm (about 5.8 by 8.3 inches)

b5paper
     176 by 250mm (about 6.9 by 9.8 inches)

executivepaper
     7.25 by 10.5 inches

legalpaper
     8.5 by 14 inches

letterpaper
     8.5 by 11 inches (the default)

When using one of the engines pdfLaTeX, LuaLaTeX, or XeLaTeX (see TeX engines), options other than letterpaper set the print area but you must also set the physical paper size.  One way to do that is to put \pdfpagewidth=\paperwidth and \pdfpageheight=\paperheight in your document's preamble.

The geometry package provides flexible ways of setting the print area and physical page size.

Miscellaneous other options:

draft
final
     Mark (draft) or do not mark (final) overfull boxes with a black box in the margin; default is final.

fleqn
     Put displayed formulas flush left; default is centered.

landscape
     Selects landscape format; default is portrait.

leqno
     Put equation numbers on the left side of equations; default is the right side.

openbib
     Use ``open'' bibliography format.

titlepage
notitlepage
     Specifies whether there is a separate page for the title information and for the abstract also, if there is one.  The default for the report class is titlepage, for the other classes it is notitlepage.

The following options are not available with the slides class.

onecolumn
twocolumn
     Typeset in one or two columns; default is onecolumn.

oneside
twoside
     Selects one- or two-sided layout; default is oneside, except that in the book class the default is twoside.

     For one-sided printing, the text is centered on the page.  For two-sided printing, the \evensidemargin (\oddsidemargin) parameter determines the distance on even (odd) numbered pages between the left side of the page and the text's left margin, with \oddsidemargin being 40% of the difference between \paperwidth and \textwidth, and \evensidemargin is the remainder.

openright
openany
     Determines if a chapter should start on a right-hand page; default is openright for book, and openany for report.

The slides class offers the option clock for printing the time at the bottom of each note.

Additional packages
===================

Load a package PKG, with the package options given in the comma-separated list OPTIONS, as here.

     \usepackage[OPTIONS]{PKG}.

To specify more than one package you can separate them with a comma, as in \usepackage{PKG1,PKG2,...}, or use multiple \usepackage commands.

Any options given in the \documentclass command that are unknown to the selected document class are passed on to the packages loaded with \usepackage.

Class and package construction
==============================

You can create new document classes and new packages.  For instance, if your memos must satisfy some local requirements, such as a standard header for each page, then you could create a new class smcmemo.cls and begin your documents with \documentclass{smcmemo}.

What separates a package from a document class is that the commands in a package are useful across classes while those in a document class are specific to that class.  Thus, a command to set page headers is for a package while a command to make the page headers say Memo from the SMC Math Department is for a class.

Inside of a class or package file you can use the at-sign @ as a character in command names without having to surround the code containing that command with \makeatletter and \makeatother.  See \makeatletter & \makeatother. This allow you to create commands that users will not accidentally redefine. Another technique is to preface class- or package-specific commands with some string to prevent your class or package from interfering with others. For instance, the class smcmemo might have commands \smc@tolist, \smc@fromlist, etc.

Class and package structure
---------------------------

A class file or package file typically has four parts.

 1. In the identification part, the file says that it is a LaTeX package or class and describes itself, using the \NeedsTeXFormat and \ProvidesClass or \ProvidesPackage commands.

 2. The preliminary declarations part declares some commands and can also load other files. Usually these commands will be those needed for the code used in the next part.  For example, an smcmemo class might be called with an option to read in a file with a list of people for the to-head, as \documentclass[mathto]{smcmemo}, and therefore needs to define a command \newcommand{\setto}[1]{\def\@tolist{#1}} used in that file.

 3. In the handle options part the class or package declares and processes its options.  Class options allow a user to start their document as \documentclass[OPTION LIST]{CLASS NAME}, to modify the behavior of the class.  An example is when you declare \documentclass[11pt]{article} to set the default document font size.

 4. Finally, in the more declarations part the class or package usually does most of its work: declaring new variables, commands and fonts, and loading other files.

Here is a starting class file, which should be saved as stub.cls where LaTeX can find it, for example in the same directory as the .tex file.

     \NeedsTeXFormat{LaTeX2e}
     \ProvidesClass{stub}[2017/07/06 stub to start building classes from]
     \DeclareOption*{\PassOptionsToClass{\CurrentOption}{article}}
     \ProcessOptions\relax
     \LoadClass{article}

It identifies itself, handles the class options via the default of passing them all to the article class, and then loads the article class to provide the basis for this class's code.

For more, see the official guide for class and package writers, the Class Guide, at http://www.latex-project.org/help/documentation/clsguide.pdf (much of the descriptions here derive from this document), or the tutorial https://www.tug.org/TUGboat/tb26-3/tb84heff.pdf.

Class and package commands
--------------------------

These are the commands designed to help writers of classes or packages.

\AtBeginDvi{specials}
     Save in a box register things that are written to the .dvi file at the beginning of the shipout of the first page of the document.

\AtEndOfClass{CODE}

\AtEndOfPackage{CODE}
     Hook to insert CODE to be executed when LaTeX finishes processing the current class or package.  You can use these hooks multiple times; the code will be executed in the order that you called it.  See also \AtBeginDocument.

\CheckCommand{CMD}[NUM][DEFAULT]{DEFINITION}

\CheckCommand*{CMD}[NUM][DEFAULT]{DEFINITION}
     Like \newcommand (see \newcommand & \renewcommand) but does not define CMD; instead it checks that the current definition of CMD is exactly as given by DEFINITION and is or is not long as expected.  A long command is a command that accepts \par within an argument.  The CMD command is expected to be long with the unstarred version of \CheckCommand.  Raises an error when the check fails.  This allows you to check before you start redefining cmd yourself that no other package has already redefined this command.

\ClassError{CLASS NAME}{ERROR TEXT}{HELP TEXT}

\PackageError{PACKAGE NAME}{ERROR TEXT}{HELP TEXT}

\ClassWarning{CLASS NAME}{WARNING TEXT}

\PackageWarning{PACKAGE NAME}{WARNING TEXT}

\ClassWarningNoLine{CLASS NAME}{WARNING TEXT}

\PackageWarningNoLine{PACKAGE NAME}{WARNING TEXT}

\ClassInfo{CLASS NAME}{INFO TEXT}

\PackageInfo{PACKAGE NAME}{INFO TEXT}

\ClassInfoNoLine{CLASS NAME}{INFO TEXT}

\PackageInfoNoLine{PACKAGE NAME}{INFO TEXT}
     Produce an error message, or warning or informational messages.

     For \ClassError and \PackageError the message is ERROR TEXT, followed by TeX's ? error prompt. If the user then asks for help by typing h, they see the HELP TEXT.

     The four warning commands are similar except that they write WARNING TEXT on the screen with no error prompt.  The four info commands write INFO TEXT only in the transcript file.  The NoLine versions do not show the number of the line generating the message, while the other versions do show that number.

     To format the messages, including the HELP TEXT: use \protect to stop a command from expanding, get a line break with \MessageBreak, and get a space with \space when a space character does not allow it, like after a command.  Note that LaTeX appends a period to the messages.

\CurrentOption
     Expands to the name of the currently-being-processed option.  Can only be used within the CODE argument of either \DeclareOption or \DeclareOption*.

\DeclareOption{OPTION}{CODE}

\DeclareOption*{CODE}
     Make an option available to a user to invoke in their \documentclass command.  For example, the smcmemo class could have an option \documentclass[logo]{smcmemo} allowing users to put the institutional logo on the first page.  The class file must contain \DeclareOption{logo}{CODE} (and later, \ProcessOptions).

     If you request an option that has not been declared, by default this will produce a warning like Unused global option(s): [badoption]. Change this behaviour with the starred version \DeclareOption*{CODE}.  For example, many classes extend an existing class, using a declaration such as \LoadClass{article}, and for passing extra options to the underlying class use code such as this.

          \DeclareOption*{%
          \PassOptionsToClass{\CurrentOption}{article}%
          }

     Another example is that the class smcmemo may allow users to keep lists of memo recipients in external files.  Then the user could invoke \documentclass[math]{smcmemo} and it will read the file math.memo.  This code handles the file if it exists and otherwise passes the option to the article class.

          \DeclareOption*{\InputIfFileExists{\CurrentOption.memo}{}{%
              \PassOptionsToClass{\CurrentOption}{article}}}

\DeclareRobustCommand{CMD}[NUM][DEFAULT]{DEFINITION}

\DeclareRobustCommand*{CMD}[NUM][DEFAULT]{DEFINITION}
     Like \newcommand and \newcommand* (see \newcommand & \renewcommand) but these declare a robust command, even if some code within the DEFINITION is fragile.  (For a discussion of robust and fragile commands see \protect.) Use this command to define new robust commands or to redefine existing commands and make them robust. Unlike \newcommand these do not give an error if macro CMD already exists; instead, a log message is put into the transcript file if a command is redefined.

     Commands defined this way are a bit less efficient than those defined using \newcommand so unless the command's data is fragile and the command is used within a moving argument, use \newcommand.

     etoolbox The etoolbox package offers the commands \newrobustcmd, \newrobustcmd*, as well as the commands \renewrobustcmd, \renewrobustcmd*, and the commands \providerobustcmd, and \providerobustcmd*.  These are similar to \newcommand, \newcommand*, \renewcommand, \renewcommand*, \providecommand, and \providecommand*, but define a robust CMD with two advantages as compared to \DeclareRobustCommand:

      1. They use the low-level e-TeX protection mechanism rather than the higher level LaTeX \protect mechanism, so they do not incur the slight loss of performance mentioned above, and

      2. They make the same distinction between \new..., \renew..., and \provide..., as the standard commands, so they do not just make a log message when you redefine CMD that already exists, in that case you need to use either \renew... or \provide... or you get an error.

\IfFileExists{FILE NAME}{TRUE CODE}{FALSE CODE}

\InputIfFileExists{FILE NAME}{TRUE CODE}{FALSE CODE}
     Execute TRUE CODE if LaTeX finds the file FILE NAME or FALSE CODE otherwise.  In the first case it executing TRUE CODE and then inputs the file.  Thus the command

          \IfFileExists{img.pdf}{%
            \includegraphics{img.pdf}}{\typeout{!! img.pdf not found}

     will include the graphic img.pdf if it is found and otherwise give a warning.

     This command looks for the file in all search paths that LaTeX uses, not only in the current directory.  To look only in the current directory do something like \IfFileExists{./filename}{TRUE CODE}{FALSE CODE}.  If you ask for a filename without a .tex extension then LaTeX will first look for the file by appending the .tex; for more on how LaTeX handles file extensions see \input.

\LoadClass[OPTIONS LIST]{CLASS NAME}[RELEASE DATE]

\LoadClassWithOptions{CLASS NAME}[RELEASE DATE]
     Load a class, as with \documentclass[OPTIONS LIST]{CLASS NAME}[RELEASE INFO].  An example is \LoadClass[twoside]{article}.

     The OPTIONS LIST, if present, is a comma-separated list.  The RELEASE DATE is optional.  If present it must have the form YYYY/MM/DD.

     If you request a RELEASE DATE and the date of the package installed on your system is earlier, then you get a warning on the screen and in the log like this.

          You have requested, on input line 4, version `2038/01/19' of
          document class article, but only version `2014/09/29 v1.4h
          Standard LaTeX document class' is available.

     The command version \LoadClassWithOptions uses the list of options for the current class.  This means it ignores any options passed to it via \PassOptionsToClass.  This is a convenience command that lets you build classes on existing ones, such as the standard article class, without having to track which options were passed.

\ExecuteOptions{OPTIONS-LIST}
     For each option OPTION in the OPTIONS-LIST, in order, this command executes the command \ds@OPTION.  If this command is not defined then that option is silently ignored.

     It can be used to provide a default option list before \ProcessOptions.  For example, if in a class file you want the default to be 11pt fonts then you could specify \ExecuteOptions{11pt}\ProcessOptions\relax.

\NeedsTeXFormat{FORMAT}[FORMAT DATE]
     Specifies the format that this class must be run under.  Often issued as the first line of a class file, and most often used as: \NeedsTeXFormat{LaTeX2e}.  When a document using that class is processed, the format name given here must match the format that is actually being run (including that the FORMAT string is case sensitive).  If it does not match then execution stops with an error like This file needs format `LaTeX2e' but this is `xxx'.

     To specify a version of the format that you know to have certain features, include the optional FORMAT DATE on which those features were implemented.  If present it must be in the form YYYY/MM/DD. If the format version installed on your system is earlier than FORMAT DATE then you get a warning like this.

          You have requested release `2038/01/20' of LaTeX, but only
          release `2016/02/01' is available.

\OptionNotUsed
     Adds the current option to the list of unused options.  Can only be used within the CODE argument of either \DeclareOption or \DeclareOption*.

\PassOptionsToClass{OPTION LIST}{CLASS NAME}

\PassOptionsToPackage{OPTION LIST}{PACKAGE NAME}
     Adds the options in the comma-separated list OPTION LIST to the options used by any future \RequirePackage or \usepackage command for package PACKAGE NAME or the class CLASS NAME.

     The reason for these commands is: you may load a package any number of times with no options but if you want options then you may only supply them when you first load the package.  Loading a package with options more than once will get you an error like Option clash for package foo. (LaTeX throws an error even if there is no conflict between the options.)

     If your own code is bringing in a package twice then you can collapse that to once, for example replacing the two \RequirePackage[landscape]{geometry} and \RequirePackage[margins=1in]{geometry} with the single command \RequirePackage[landscape,margins=1in]{geometry}.

     However, imagine that you are loading firstpkg and inside that package it loads secondpkg, and you need the second package to be loaded with option draft.  Then before doing the first package you must queue up the options for the second package, like this.

          \PassOptionsToPackage{draft}{secondpkg}
          \RequirePackage{firstpkg}

     (If firstpkg.sty loads an option in conflict with what you want then you may have to alter its source.)

     These commands are useful for general users as well as class and package writers.  For instance, suppose a user wants to load the graphicx package with the option draft and also wants to use a class foo that loads the graphicx package, but without that option. The user could start their LaTeX file with \PassOptionsToPackage{draft}{graphicx}\documentclass{foo}.

\ProcessOptions

\ProcessOptions*\@OPTIONS
     Execute the code for each option that the user has invoked.  Include it in the class file as \ProcessOptions\relax (because of the existence of the starred command).

     Options come in two types.  Local options have been specified for this particular package in the OPTIONS argument of \PassOptionsToPackage{OPTIONS}, \usepackage[OPTIONS], or \RequirePackage[OPTIONS].  Global options are those given by the class user in \documentclass[OPTIONS] (If an option is specified both locally and globally then it is local.)

     When \ProcessOptions is called for a package pkg.sty, the following happens:

      1. For each option OPTION so far declared with \DeclareOption, it looks to see if that option is either a global or a local option for pkg. If so then it executes the declared code.  This is done in the order in which these options were given in pkg.sty.

      2. For each remaining local option, it executes the command \ds@OPTION if it has been defined somewhere (other than by a \DeclareOption); otherwise, it executes the default option code given in \DeclareOption*. If no default option code has been declared then it gives an error message.  This is done in the order in which these options were specified.

     When \ProcessOptions is called for a class it works in the same way except that all options are local, and the default CODE for \DeclareOption* is \OptionNotUsed rather than an error.

     The starred version \ProcessOptions* executes the options in the order specified in the calling commands, rather than in the order of declaration in the class or package. For a package this means that the global options are processed first.

\ProvidesClass{CLASS NAME}[RELEASE DATE BRIEF ADDITIONAL INFORMATION]

\ProvidesClass{CLASS NAME}[RELEASE DATE]

\ProvidesPackage{PACKAGE NAME}[RELEASE DATE BRIEF ADDITIONAL INFORMATION]

\ProvidesPackage{PACKAGE NAME}[RELEASE DATE]
     Identifies the class or package, printing a message to the screen and the log file.

     When you load a class or package, for example with \documentclass{smcmemo} or \usepackage{test}, LaTeX inputs a file.  If the name of the file does not match the class or package name declared in it then you get a warning.  Thus, if you invoke \documentclass{smcmemo}, and the file smcmemo.cls has the statement \ProvidesClass{xxx} then you get a warning like You have requested document class `smcmemo', but the document class provides 'xxx'.  This warning does not prevent LaTeX from processing the rest of the class file normally.

     If you include the optional argument then you must include a date, before any spaces, of the form YYYY/MM/DD. The rest of the optional argument is free-form, although it traditionally identifies the class, and is written to the screen during compilation and to the log file.  Thus, if your file smcmemo.cls contains the line \ProvidesClass{smcmemo}[2008/06/01 v1.0 SMC memo class] and your document's first line is \documentclass{smcmemo} then you will see Document Class: smcmemo 2008/06/01 v1.0 SMC memo class.

     The date in the optional argument allows class and package users to ask to be warned if the version of the class or package is earlier than RELEASE DATE.  For instance, a user could enter \documentclass{smcmemo}[2018/10/12] or \usepackage{foo}[[2017/07/07]] to require a class or package with certain features by specifying that it must be released no earlier than the given date.  (Although, in practice package users only rarely include a date, and class users almost never do.)

\ProvidesFile{FILE NAME}[ADDITIONAL INFORMATION]
     Declare a file other than the main class and package files, such as configuration files or font definition files.  Put this command in that file and you get in the log a string like File: test.config 2017/10/12 config file for test.cls for FILE NAME equal to test.config and ADDITIONAL INFORMATION equal to 2017/10/12 config file for test.cls.

\RequirePackage[OPTION LIST]{PACKAGE NAME}[RELEASE DATE]

\RequirePackageWithOptions{PACKAGE NAME}[RELEASE DATE]
     Load a package, like the command \usepackage (see Additional packages). The LaTeX development team strongly recommends use of these commands over Plain TeX's \input; see the Class Guide.  An example is \RequirePackage[landscape,margin=1in]{geometry}.

     The OPTION LIST, if present, is a comma-separated list.  The RELEASE DATE, if present, must have the form YYYY/MM/DD.  If the release date of the package as installed on your system is earlier than RELEASE DATE then you get a warning like You have requested, on input line 9, version `2017/07/03' of package jhtest, but only version `2000/01/01' is available.

     The \RequirePackageWithOptions version uses the list of options for the current class.  This means it ignores any options passed to it via \PassOptionsToClass.  This is a convenience command to allow easily building classes on existing ones without having to track which options were passed.

     The difference between \usepackage and \RequirePackage is small.  The \usepackage command is intended for the document file while \RequirePackage is intended for package and class files. Thus, using \usepackage before the \documentclass command causes LaTeX to give error like \usepackage before \documentclass, but you can use \RequirePackage there.

Fonts
*****

old name

Two important aspects of selecting a font are specifying a size and a style.  The LaTeX commands for doing this are described here.

Font styles
===========

The following type style commands are supported by LaTeX.

In the table below the listed commands, the \text...  commands, is used with an argument, as in \textit{TEXT}.  This is the preferred form.  But shown after it, in parenthesis, is the corresponding declaration form, which is sometimes useful.  This form takes no arguments, as in {\itshape TEXT}.  The scope of the declaration form lasts until the next type style command or the end of the current group.  In addition, each has an environment form such as \begin{itshape}...\end{itshape}.

These commands, in both the argument form and the declaration form, are cumulative; for instance you can get bold sans serif by saying either of \sffamily\bfseries or \bfseries\sffamily.

One advantage of these commands is that they automatically insert italic corrections if needed (see \/).  Specifically, they insert the italic correction unless the following character is in the list \nocorrlist, which by default consists of a period and a comma. To suppress the automatic insertion of italic correction, use \nocorr at the start or end of the command argument, such as \textit{\nocorr text} or \textsc{text \nocorr}.

\textrm (\rmfamily)
     Roman.

\textit (\itshape)
     Italics.

\textmd (\mdseries)
     Medium weight (default).

\textbf (\bfseries)
     Boldface.

\textup (\upshape)
     Upright (default).

\textsl (\slshape)
     Slanted.

\textsf (\sffamily)
     Sans serif.

\textsc (\scshape)
     Small caps.

\texttt (\ttfamily)
     Typewriter.

\textnormal (\normalfont)
     Main document font.

Although it also changes fonts, the \emph{TEXT} command is semantic, for text to be emphasized, and should not be used as a substitute for \textit.  For example, \emph{START TEXT \emph{MIDDLE TEXT} END TEXT} will result in the START TEXT and END TEXT in italics, but MIDDLE TEXT will be in roman.

LaTeX also provides the following commands, which unconditionally switch to the given style, that is, are not cumulative.  They are used as declarations: {\CMD...} instead of \CMD{...}.

(The unconditional commands below are an older version of font switching. The earlier commands are an improvement in most circumstances. But sometimes an unconditional font switch is precisely what you want.)

\bf
     Switch to bold face.

\cal
     Switch to calligraphic letters for math.

\it
     Italics.

\rm
     Roman.

\sc
     Small caps.

\sf
     Sans serif.

\sl
     Slanted (oblique).

\tt
     Typewriter (monospace, fixed-width).

The \em command is the unconditional version of \emph.

The following commands are for use in math mode.  They are not cumulative, so \mathbf{\mathit{SYMBOL}} does not create a boldface and italic SYMBOL; instead, it will just be in italics.  This is because typically math symbols need consistent typographic treatment, regardless of the surrounding environment.

\mathrm
     Roman, for use in math mode.

\mathbf
     Boldface, for use in math mode.

\mathsf
     Sans serif, for use in math mode.

\mathtt
     Typewriter, for use in math mode.

\mathit
(\mit)
     Italics, for use in math mode.

\mathnormal
     For use in math mode, e.g., inside another type style declaration.

\mathcal
     Calligraphic letters, for use in math mode.

In addition, the command \mathversion{bold} can be used for switching to bold letters and symbols in formulas. \mathversion{normal} restores the default.

Finally, the command \oldstylenums{NUMERALS} will typeset so-called ``old-style'' numerals, which have differing heights and depths (and sometimes widths) from the standard ``lining'' numerals, which all have the same height as uppercase letters.  LaTeX's default fonts support this, and will respect \textbf (but not other styles; there are no italic old-style numerals in Computer Modern).  Many other fonts have old-style numerals also; sometimes the textcomp package must be loaded, and sometimes package options are provided to make them the default.  FAQ entry: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=osf.

Font sizes
==========

The following standard type size commands are supported by LaTeX. The table shows the command name and the corresponding actual font size used (in points) with the 10pt, 11pt, and 12pt document size options, respectively (see Document class options).

Command    10pt    11pt    12pt
\tiny
5            6            6
\scriptsize
7            8            8
\footnotesize
8            9            10
\small
9            10           10.95
\normalsize (default)
10           10.95        12
\large
12           12           14.4
\Large
14.4         14.4         17.28
\LARGE
17.28        17.28        20.74
\huge
20.74        20.74        24.88
\Huge
24.88        24.88        24.88

The commands are listed here in declaration forms. You use them by declaring them, as with this example.

     \begin{quotation} \small
       The Tao that can be named is not the eternal Tao.
     \end{quotation}

The scope of the \small lasts until the end of the quotation environment.  It would also end at the next type style command or the end of the current group, so you could enclose it in extra curly braces {\small We are here, we are here, we are here!}.  You can instead use the environment form of these commands; for instance, \begin{tiny}...\end{tiny}.

Low-level font commands
=======================

These commands are primarily intended for writers of macros and packages.  The commands listed here are only a subset of the available ones.

\fontencoding{ENCODING}
     Select the font encoding, the encoding of the output font. There are a large number of valid encodings.  The most common are OT1, Knuth's original encoding for Computer Modern (the default), and T1, also known as the Cork encoding, which has support for the accented characters used by the most widespread European languages (German, French, Italian, Polish and others), which allows TeX to hyphenate words containing accented letters. For more, see https://ctan.org/pkg/encguide.

\fontfamily{FAMILY}
     Select the font family.  The web page http://www.tug.dk/FontCatalogue/ provides one way to browse through many of the fonts easily used with LaTeX.  Here are examples of some common families.

     pag
     Avant Garde
     fvs
     Bitstream Vera Sans
     pbk
     Bookman
     bch
     Charter
     ccr
     Computer Concrete
     cmr
     Computer Modern
     cmss
     Computer Modern Sans Serif
     cmtt
     Computer Modern Typewriter
     pcr
     Courier
     phv
     Helvetica
     fi4
     Inconsolata
     lmr
     Latin Modern
     lmss
     Latin Modern Sans
     lmtt
     Latin Modern Typewriter
     pnc
     New Century Schoolbook
     ppl
     Palatino
     ptm
     Times
     uncl
     Uncial
     put
     Utopia
     pzc
     Zapf Chancery

\fontseries{SERIES}
     Select the font series.  A series combines a weight and a width.  Typically, a font supports only a few of the possible combinations.  Some common combined series values include:

     m
     Medium (normal)
     b
     Bold
     c
     Condensed
     bc
     Bold condensed
     bx
     Bold extended

     The possible values for weight, individually, are:

     ul
     Ultra light
     el
     Extra light
     l
     Light
     sl
     Semi light
     m
     Medium (normal)
     sb
     Semi bold
     b
     Bold
     eb
     Extra bold
     ub
     Ultra bold

     The possible values for width, individually, are (the meaning and relationship of these terms varies with individual typefaces):

     uc
     Ultra condensed
     ec
     Extra condensed
     c
     Condensed
     sc
     Semi condensed
     m
     Medium
     sx
     Semi expanded
     x
     Expanded
     ex
     Extra expanded
     ux
     Ultra expanded

     When forming the SERIES string from the weight and width, drop the m that stands for medium weight or medium width, unless both weight and width are m, in which case use just one (m).

\fontshape{SHAPE}
     Select font shape. Valid shapes are:

     n
     Upright (normal)
     it
     Italic
     sl
     Slanted (oblique)
     sc
     Small caps
     ui
     Upright italics
     ol
     Outline

     The two last shapes are not available for most font families, and small caps are often missing as well.

\fontsize{SIZE}{SKIP}
     Set the font size and the line spacing.  The unit of both parameters defaults to points (pt).  The line spacing is the nominal vertical space between lines, baseline to baseline.  It is stored in the parameter \baselineskip.  The default \baselineskip for the Computer Modern typeface is 1.2 times the \fontsize. Changing \baselineskip directly is inadvisable since its value is reset every time a size change happens; see \baselinestretch, next.

\baselinestretch
     LaTeX multiplies the line spacing by the value of the \baselinestretch parameter; the default factor is 1.  A change takes effect when \selectfont (see below) is called.  You can make a line skip change happen for the entire document, for instance doubling it, by doing \renewcommand{\baselinestretch}{2.0} in the preamble.

     However, the best way to double-space a document is to use the setspace package.  In addition to offering a number of spacing options, this package keeps the line spacing single-spaced in places where that is typically desirable, such as footnotes and figure captions.  See the package documentation.

\linespread{FACTOR}
     Equivalent to \renewcommand{\baselinestretch}{FACTOR}, and therefore must be followed by \selectfont to have any effect. Best specified in the preamble, or use the setspace package, as just described.

\selectfont
     The effects of the font commands described above do not happen until \selectfont is called, as in \fontfamily{FAMILYNAME}\selectfont.  It is often useful to put this in a macro:

     \newcommand*{\myfont}{\fontfamily{FAMILYNAME}\selectfont}

     (see \newcommand & \renewcommand).

\usefont{ENC}{FAMILY}{SERIES}{SHAPE}
     The same as invoking \fontencoding, \fontfamily, \fontseries and \fontshape with the given parameters, followed by \selectfont.  For example:

          \usefont{ot1}{cmr}{m}{n}

Layout
******

Commands for controlling the general page layout.

\onecolumn
==========

Synopsis:

     \onecolumn

Start a new page and produce single-column output.  If the document is given the class option onecolumn then this is the default behavior (see Document class options).  This command is fragile (see \protect).

\twocolumn
==========

Synopses:

     \twocolumn
     \twocolumn[PRELIM ONE COLUMN TEXT]

Start a new page and produce two-column output. If the document is given the class option twocolumn then this is the default (see Document class options).  This command is fragile (see \protect).

If the optional PRELIM ONE COLUMN TEXT argument is present, it is typeset in one-column mode before the two-column typesetting starts.

These parameters control typesetting in two-column output:

\columnsep
     The distance between columns. The default is 35pt.  Change it with a command such as \setlength{\columnsep}{40pt} You must change it before the two column environment starts; in the preamble is a good place.

\columnseprule
     The width of the rule between columns. The rule appears halfway between the two columns.  The default is 0pt, meaning that there is no rule. Change it with a command such as \setlength{\columnseprule}{0.4pt}, before the two-column environment starts.

\columnwidth
     The width of a single column.  In one-column mode this is equal to \textwidth.  In two-column mode by default LaTeX sets the width of each of the two columns to be half of \textwidth minus \columnsep.

In a two-column document, the starred environments table* and figure* are two columns wide, whereas the unstarred environments table and figure take up only one column (see figure and see table). LaTeX places starred floats at the top of a page. The following parameters control float behavior of two-column output.

\dbltopfraction
     The maximum fraction at the top of a two-column page that may be occupied by two-column wide floats.  The default is 0.7, meaning that the height of a table* or figure* environment must not exceed 0.7\textheight .  If the height of your starred float environment exceeds this then you can take one of the following actions to prevent it from floating all the way to the back of the document:

       * Use the [tp] location specifier to tell LaTeX to try to put the bulky float on a page by itself, as well as at the top of a page.

       * Use the [t!] location specifier to override the effect of \dbltopfraction for this particular float.

       * Increase the value of \dbltopfraction to a suitably large number, to avoid going to float pages so soon.

     You can redefine it, as with \renewcommand{\dbltopfraction}{0.9}.

\dblfloatpagefraction
     For a float page of two-column wide floats, this is the minimum fraction that must be occupied by floats, limiting the amount of blank space. LaTeX's default is 0.5.  Change it with \renewcommand.

\dblfloatsep
     On a float page of two-column wide floats, this length is the distance between floats, at both the top and bottom of the page.  The default is 12pt plus2pt minus2pt for a document set at 10pt or 11pt, and 14pt plus2pt minus4pt for a document set at 12pt.

\dbltextfloatsep
     This length is the distance between a multi-column float at the top or bottom of a page and the main text.  The default is 20pt plus2pt minus4pt.

\dbltopnumber
     On a float page of two-column wide floats, this counter gives the maximum number of floats allowed at the top of the page.  The LaTeX default is 2.

This example uses \twocolumn's optional argument of to create a title that spans the two-column article:

     \documentclass[twocolumn]{article}
     \newcommand{\authormark}[1]{\textsuperscript{#1}}
     \begin{document}
     \twocolumn[{% inside this optional argument goes one-column text
       \centering
       \LARGE The Title \\[1.5em]
       \large Author One\authormark{1},
              Author Two\authormark{2},
              Author Three\authormark{1} \\[1em]
       \normalsize
       \begin{tabular}{p{.2\textwidth}@{\hspace{2em}}p{.2\textwidth}}
         \authormark{1}Department one  &\authormark{2}Department two \\
          School one                   &School two
       \end{tabular}\\[3em] % space below title part
       }]

     Two column text here.

\flushbottom
============

Make all pages in the documents after this declaration have the same height, by stretching the vertical space where necessary to fill out the page.  This is most often used when making two-sided documents since the differences in facing pages can be glaring.

If TeX cannot satisfactorily stretch the vertical space in a page then you get a message like Underfull \vbox (badness 10000) has occurred while \output is active.  If you get that, one option is to change to \raggedbottom (see \raggedbottom).  Alternatively, you can adjust the textheight to make compatible pages, or you can add some vertical stretch glue between lines or between paragraphs, as in \setlength{\parskip}{0ex plus0.1ex}.  Your last option is to, in a final editing stage, adjust the height of individual pages (see \enlargethispage).

The \flushbottom state is the default only if you select the twoside document class option (see Document class options).

\raggedbottom
=============

Make all later pages the natural height of the material on that page; no rubber vertical lengths will be stretched.  Thus, in a two-sided document the facing pages may be different heights.  This command can go at any point in the document body.  See \flushbottom.

This is the default unless you select the twoside document class option (see Document class options).

Page layout parameters
======================

\columnsep
\columnseprule
\columnwidth
     The distance between the two columns, the width of a rule between the columns, and the width of the columns, when the document class option twocolumn is in effect (see Document class options). See \twocolumn.

\headheight
     Height of the box that contains the running head.  The default in the article, report, and book classes is 12pt, at all type sizes.

\headsep
     Vertical distance between the bottom of the header line and the top of the main text.  The default in the article and report classes is 25pt.  In the book class the default is: if the document is set at 10pt then it is 0.25in, and at 11pt and 12pt it is 0.275in.

\footskip
     Distance from the baseline of the last line of text to the baseline of the page footer.  The default in the article and report classes is 30pt.  In the book class the default is: when the type size is 10pt the default is 0.35in, while at 11pt it is 0.38in, and at 12pt it is 30pt.

\linewidth
     Width of the current line, decreased for each nested list (see list).  That is, the nominal value for \linewidth is to equal \textwidth but for each nested list the \linewidth is decreased by the sum of that list's \leftmargin and \rightmargin (see itemize).

\marginparpush
\marginsep
\marginparwidth
     The minimum vertical space between two marginal notes, the horizontal space between the text body and the marginal notes, and the horizontal width of the notes.

     Normally marginal notes appear on the outside of the page, but the declaration \reversemarginpar changes that (and \normalmarginpar changes it back).

     The defaults for \marginparpush in both book and article classes are: 7pt if the document is set at 12pt, and 5pt if the document is set at 11pt or 10pt.

     For \marginsep, in article class the default is 10pt except if the document is set at 10pt and in two-column mode where the default is 11pt.

     For \marginsep in book class the default is 10pt in two-column mode and 7pt in one-column mode.

     For \marginparwidth in both book and article classes, in two-column mode the default is 60% of \paperwidth - \textwidth, while in one-column mode it is 50% of that distance.

\oddsidemargin
\evensidemargin
     The \oddsidemargin is the extra distance between the left side of the page and the text's left margin, on odd-numbered pages when the document class option twoside is chosen and on all pages when oneside is in effect.  When twoside is in effect, on even-numbered pages the extra distance on the left is evensidemargin.

     LaTeX's default is that \oddsidemargin is 40% of the difference between \paperwidth and \textwidth, and \evensidemargin is the remainder.

\paperheight
     The height of the paper, as distinct from the height of the print area. Normally set with a document class option, as in \documentclass[a4paper]{article} (see Document class options).

\paperwidth
     The width of the paper, as distinct from the width of the print area. Normally set with a document class option, as in \documentclass[a4paper]{article} (see Document class options).

\textheight
     The normal vertical height of the page body.  If the document is set at a nominal type size of 10pt then for an article or report the default is 43\baselineskip, while for a book it is 41\baselineskip.  At a type size of 11pt the default is 38\baselineskip for all document classes.  At 12pt it is 36\baselineskip for all classes.

\textwidth
     The full horizontal width of the entire page body.  For an article or report document, the default is 345pt when the chosen type size is 10pt, the default is 360pt at 11pt, and it is 390pt at 12pt.  For a book document, the default is 4.5in at a type size of 10pt, and 5in at 11pt or 12pt.

     In multi-column output, \textwidth remains the width of the entire page body, while \columnwidth is the width of one column (see \twocolumn).

     In lists (see list), \textwidth remains the width of the entire page body (and \columnwidth the width of the entire column), while \linewidth may decrease for nested lists.

     Inside a minipage (see minipage) or \parbox (see \parbox), all the width-related parameters are set to the specified width, and revert to their normal values at the end of the minipage or \parbox.

\hsize
     This entry is included for completeness: \hsize is the TeX primitive parameter used when text is broken into lines.  It should not be used in normal LaTeX documents.

\topmargin
     Space between the top of the TeX page (one inch from the top of the paper, by default) and the top of the header.  The value is computed based on many other parameters: \paperheight - 2in - \headheight - \headsep - \textheight - \footskip, and then divided by two.

\topskip
     Minimum distance between the top of the page body and the baseline of the first line of text.  For the standard classes, the default is the same as the font size, e.g., 10pt at a type size of 10pt.

Floats
======

Some typographic elements, such as figures and tables, cannot be broken across pages.  They must be typeset outside of the normal flow of text, for instance floating to the top of a later page.

LaTeX can have a number of different classes of floating material. The default is the two classes, figure (see figure) and table (see table), but you can create a new class with the package float.

Within any one float class LaTeX always respects the order, so that the first figure in a document source must be typeset before the second figure.  However, LaTeX may mix the classes, so it can happen that while the first table appears in the source before the first figure, it appears in the output after it.

The placement of floats is subject to parameters, given below, that limit the number of floats that can appear at the top of a page, and the bottom, etc. If so many floats are queued that the limits prevent them all from fitting on a page then LaTeX places what it can and defers the rest to the next page.  In this way, floats may end up being typeset far from their place in the source.  In particular, a float that is big may migrate to the end of the document. In which event, because all floats in a class must appear in sequential order, every following float in that class also appears at the end.

In addition to changing the parameters, for each float you can tweak where the float placement algorithm tries to place it by using its PLACEMENT argument.  The possible values are a sequence of the letters below. The default for both figure and table, in both article and book classes, is tbp.

t
     (Top)---at the top of a text page.

b
     (Bottom)---at the bottom of a text page.  (However, b is not allowed for full-width floats (figure*) with double-column output.  To ameliorate this, use the stfloats or dblfloatfix package, but see the discussion at caveats in the FAQ: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=2colfloat.

h
     (Here)---at the position in the text where the figure environment appears.  However, h is not allowed by itself; t is automatically added.

     To absolutely force a float to appear ``here'', you can \usepackage{float} and use the H specifier which it defines.  For further discussion, see the FAQ entry at http://www.tex.ac.uk/cgi-bin/texfaq2html?label=figurehere.

p
     (Page of floats)---on a separate float page, which is a page containing no text, only floats.

!
     Used in addition to one of the above; for this float only, LaTeX ignores the restrictions on both the number of floats that can appear and the relative amounts of float and non-float text on the page. The ! specifier does not mean ``put the float here''; see above.

Note: the order in which letters appear in the PLACEMENT argument does not change the order in which LaTeX tries to place the float; for instance, btp has the same effect as tbp.  All that PLACEMENT does is that if a letter is not present then the algorithm does not try that location.  Thus, LaTeX's default of tbp is to try every location except placing the float where it occurs in the source.

To prevent LaTeX from moving floats to the end of the document or a chapter you can use a \clearpage command to start a new page and insert all pending floats. If a pagebreak is undesirable then you can use the afterpage package and issue \afterpage{\clearpage}.  This will wait until the current page is finished and then flush all outstanding floats.

LaTeX can typeset a float before where it appears in the source (although on the same output page) if there is a t specifier in the PLACEMENT parameter.  If this is not desired, and deleting the t is not acceptable as it keeps the float from being placed at the top of the next page, then you can prevent it by either using the flafter package or using the command \suppressfloats[t], which causes floats for the top position on this page to moved to the next page.

Parameters relating to fractions of pages occupied by float and non-float text (change them with \renewcommand{PARAMETER}{DECIMAL BETWEEN 0 AND 1}):

\bottomfraction
     The maximum fraction of the page allowed to be occupied by floats at the bottom; default .3.

\floatpagefraction
     The minimum fraction of a float page that must be occupied by floats; default .5.

\textfraction
     Minimum fraction of a page that must be text; if floats take up too much space to preserve this much text, floats will be moved to a different page.  The default is .2.

\topfraction
     Maximum fraction at the top of a page that may be occupied before floats; default .7.

Parameters relating to vertical space around floats (change them with a command of the form \setlength{PARAMETER}{LENGTH EXPRESSION}):

\floatsep
     Space between floats at the top or bottom of a page; default 12pt plus2pt minus2pt.

\intextsep
     Space above and below a float in the middle of the main text; default 12pt plus2pt minus2pt for 10 point and 11 point documents, and 14pt plus4pt minus4pt for 12 point documents.

\textfloatsep
     Space between the last (first) float at the top (bottom) of a page; default 20pt plus2pt minus4pt.

Counters relating to the number of floats on a page (change them with a command of the form \setcounter{CTRNAME}{NATURAL NUMBER}):

bottomnumber
     Maximum number of floats that can appear at the bottom of a text page; default 1.

dbltopnumber
     Maximum number of full-sized floats that can appear at the top of a two-column page; default 2.

topnumber
     Maximum number of floats that can appear at the top of a text page; default 2.

totalnumber
     Maximum number of floats that can appear on a text page; default 3.

The principal TeX FAQ entry relating to floats http://www.tex.ac.uk/cgi-bin/texfaq2html?label=floats contains suggestions for relaxing LaTeX's default parameters to reduce the problem of floats being pushed to the end.  A full explanation of the float placement algorithm is in Frank Mittelbach's article ``How to influence the position of float environments like figure and table in LaTeX?'' (http://latex-project.org/papers/tb111mitt-float.pdf).

Sectioning
**********

Structure your text into divisions: parts, chapters, sections, etc.  All sectioning commands have the same form, one of:

     SECTIONING-COMMAND{TITLE}
     SECTIONING-COMMAND*{TITLE}
     SECTIONING-COMMAND[TOC-TITLE]{TITLE}

For instance, declare the start of a subsection as with \subsection{Motivation}.

The table has each SECTIONING-COMMAND in LaTeX.  All are available in all of LaTeX's standard document classes book, report, and article, except that \chapter is not available in article.

Sectioning unit    Command    Level
Part
\part    -1 (book, report), 0 (article)
Chapter
\chapter     0
Section
\section     1
Subsection
\subsection     2
Subsubsection
\subsubsection     3
Paragraph
\paragraph     4
Subparagraph
\subparagraph     5

All these commands have a *-form that prints TITLE as usual but is not numbered and does not make an entry in the table of contents. An example of using this is for an appendix in an article .  The input \appendix\section{Appendix} gives the output A Appendix (see \appendix).  You can lose the numbering A by instead entering \section*{Appendix} (articles often omit a table of contents and have simple page headers so the other differences from the \section command may not matter).

The section title TITLE provides the heading in the main text, but it may also appear in the table of contents and in the running head or foot (see Page styles).  You may not want the same text in these places as in the main text.  All of these commands have an optional argument TOC-TITLE for these other places.

The level number in the table above determines which sectional units are numbered, and which appear in the table of contents.  If the sectioning command's LEVEL is less than or equal to the value of the counter secnumdepth then the titles for this sectioning command will be numbered (see Sectioning/secnumdepth).  And, if LEVEL is less than or equal to the value of the counter tocdepth then the table of contents will have an entry for this sectioning unit (see Sectioning/tocdepth).

LaTeX expects that before you have a \subsection you will have a \section and, in a book, that before a \section you will have a \chapter.  Otherwise you can get a something like a subsection numbered 3.0.1.

Two counters relate to the appearance of sectioning commands.

secnumdepth
     Controls which sectioning commands are numbered.  Suppress numbering of sectioning at any depth greater than LEVEL \setcounter{secnumdepth}{LEVEL} (see \setcounter).  See the above table for the level numbers.  For instance, if the secnumdepth is 1 in an article then a \section{Introduction} command will produce output like 1 Introduction while \subsection{Discussion} will produce output like Discussion, without the number. LaTeX's default secnumdepth is 3 in article class and  2 in the book and report classes.

tocdepth
     Controls which sectioning units are listed in the table of contents. The setting \setcounter{tocdepth}{LEVEL} makes the sectioning units at LEVEL be the smallest ones listed (see \setcounter).  See the above table for the level numbers.  For instance, if tocdepth is 1 then the table of contents will list sections but not subsections.  LaTeX's default secnumdepth is 3 in article class and  2 in the book and report classes.

\part
=====

Synopsis, one of:

     \part{TITLE}
     \part*{TITLE}
     \part[TOC-TITLE]{TITLE}

Start a document part.  The standard LaTeX classes book, report, and article, all have this command.

This produces a document part, in a book.

     \part{VOLUME I \\
            PERSONAL MEMOIRS OF  U.\ S.\ GRANT}
     \chapter{ANCESTRY--BIRTH--BOYHOOD.}
     My family is American, and has been for generations,
     in all its branches, direct and collateral.

In each standard class the \part command outputs a part number such as Part I, alone on its line, in boldface, and in large type.  Then LaTeX outputs TITLE, also alone on its line, in bold and in even larger type.  In class book, the LaTeX default puts each part alone on its own page. If the book is two-sided then LaTeX will skip a page if needed to have the new part on an odd-numbered page.  In report it is again alone on a page, but LaTeX won't force it onto an odd-numbered page.  In an article LaTeX does not put it on a fresh page, but instead outputs the part number and part title onto the main document page.

The * form shows TITLE but it does not show the part number, does not increment the part counter, and produces no table of contents entry.

The optional argument TOC-TITLE will appear as the part title in the table of contents (see Table of contents etc.) and in running headers (see Page styles).  If it is not present then TITLE will be there.  This example puts a line break in TITLE but leaves out the break in the table of contents.

     \part[Up from the bottom; my life]{Up from the bottom\\ my life}

For determining which sectional units are numbered and which appear in the table of contents, the level number of a part is -1 (see Sectioning/secnumdepth and see Sectioning/tocdepth).

In the class article, if a paragraph immediately follows the part title then it is not indented.  To get an indent you can use the package indentfirst.

One package to change the behavior of \part is titlesec. See its documentation on CTAN.

\chapter
========

Synopsis, one of:

     \chapter{TITLE}
     \chapter*{TITLE}
     \chapter[TOC-TITLE]{TITLE}

Start a chapter.  The standard LaTeX classes book and report have this command but article does not.

This produces a chapter.

     \chapter{Loomings}
     Call me Ishmael.
     Some years ago---never mind how long precisely---having little or no
     money in my purse, and nothing particular to interest me on shore, I
     thought I would sail about a little and see the watery part of
     the world.

The LaTeX default starts each chapter on a fresh page, an odd-numbered page if the document is two-sided.  It produces a chapter number such as Chapter 1 in large boldface type (the size is \huge).  It then puts TITLE on a fresh line, in boldface type that is still larger (size \Huge).  It also increments the chapter counter, adds an entry to the table of contents (see Table of contents etc.), and sets the running header information (see Page styles).

The * form shows TITLE on a fresh line, in boldface. But it does not show the chapter number, does not increment the chapter counter, produces no table of contents entry, and does not affect the running header.  (If you use the page style headings in a two-sided document then the header will be from the prior chapter.)  This example illustrates.

     \chapter*{Preamble}

The optional argument TOC-TITLE will appear as the chapter title in the table of contents (see Table of contents etc.) and in running headers (see Page styles).  If it is not present then TITLE will be there.  This shows the full name in the chapter title,

     \chapter[Weyl]{Hermann Klaus Hugo (Peter) Weyl (1885--1955)}

but only Weyl on the contents page.  This puts a line break in the title but that doesn't work well with running headers so it omits the break in the contents

     \chapter[Given it all\\ my story]{Given it all\\ my story}

For determining which sectional units are numbered and which appear in the table of contents, the level number of a chapter is 0 (see Sectioning/secnumdepth and see Sectioning/tocdepth).

The paragraph that follows the chapter title is not indented, as is a standard typographical practice.  To get an indent use the package indentfirst.

You can change what is shown for the chapter number.  To change it to something like Lecture 1, put in the preamble either \renewcommand{\chaptername}{Lecture} or this (see \makeatletter & \makeatother).

     \makeatletter
     \renewcommand{\@chapapp}{Lecture}
     \makeatother

To make this change because of the primary language for the document, see the package babel.

In a two-sided document LaTeX puts a chapter on odd-numbered page, if necessary leaving an even-numbered page that is blank except for any running headers.  To make that page completely blank, see \clearpage & \cleardoublepage.

To change the behavior of the \chapter command, you can copy its definition from the LaTeX format file and make adjustments.  But there are also many packages on CTAN that address this.  One is titlesec.  See its documentation, but the example below gives a sense of what it can do.

     \usepackage{titlesec}   % in preamble
     \titleformat{\chapter}
       {\Huge\bfseries}  % format of title
       {}                % label, such as 1.2 for a subsection
       {0pt}             % length of separation between label and title
       {}                % before-code hook

This omits the chapter number Chapter 1 from the page but unlike \chapter* it keeps the chapter in the table of contents and the running headers.

\section
========

Synopsis, one of:

     \section{TITLE}
     \section*{TITLE}
     \section[TOC-TITLE]{TITLE}

Start a section.  The standard LaTeX classes article, book, and report all have this command.

This produces a section.

     In this Part we tend to be more interested in the function,
     in the input-output behavior,
     than in the details of implementing that behavior.

     \section{Turing machines}
     Despite this desire to downplay implementation,
     we follow the approach of A~Turing that the
     first step toward defining the set of computable functions
     is to reflect on the details of what mechanisms can do.

For the standard LaTeX classes book and report the default output is like 1.2 TITLE (for chapter 1, section 2), alone on its line and flush left, in boldface and a larger type (the type size is \Large).  The same holds in article except that there are no chapters in that class so it looks like 2 TITLE.

The * form shows TITLE. But it does not show the section number, does not increment the section counter, produces no table of contents entry, and does not affect the running header.  (If you use the page style headings in a two-sided document then the header will be from the prior section.)

The optional argument TOC-TITLE will appear as the section title in the table of contents (see Table of contents etc.) and in running headers (see Page styles).  If it is not present then TITLE will be there.  This shows the full name in the title of the section,

     \section[Elizabeth~II]{Elizabeth the Second,
       by the Grace of God of the United Kingdom,
       Canada and Her other Realms and Territories Queen,
       Head of the Commonwealth, Defender of the Faith.}

but only Elizabeth II on the contents page and in the headers. This has a line break in TITLE but that does not work with headers so it is omitted from the contents and headers.

     \section[Truth is, I cheated; my life story]{Truth is,
       I cheated\\my life story}

For determining which sectional units are numbered and which appear in the table of contents, the level number of a section is 1 (see Sectioning/secnumdepth and see Sectioning/tocdepth).

The paragraph that follows the section title is not indented, as is a standard typographical practice.  One way to get an indent is to use the package indentfirst.

In general, to change the behavior of the \section command, there are a number of options.  One is the \@startsection command (see \@startsection).  There are also many packages on CTAN that address this, including titlesec.  See the documentation but the example below gives a sense of what they can do.

     \usepackage{titlesec}   % in preamble
     \titleformat{\section}
       {\normalfont\Large\bfseries}  % format of title
       {\makebox[1pc][r]{\thesection\hspace{1pc}}} % label
       {0pt}                   % length of separation between label and title
       {}                      % before-code hook
     \titlespacing*{\section}
       {-1pc}{18pt}{10pt}[10pc]

That puts the section number in the margin.

\subsection
===========

Synopsis, one of:

     \subsection{TITLE}
     \subsection*{TITLE}
     \subsection[TOC-TITLE]{TITLE}

Start a subsection.  The standard LaTeX classes article, book, and report all have this command.

This produces a subsection.

     We will show that there are more functions than Turing machines and that
     therefore some functions have no associated machine.

     \subsection{Cardinality} We will begin with two paradoxes that
     dramatize the challenge to our intuition posed by comparing the sizes of
     infinite sets.

For the standard LaTeX classes book and report the default output is like 1.2.3 TITLE (for chapter 1, section 2, subsection 3), alone on its line and flush left, in boldface and a larger type (the type size is \large).  The same holds in article except that there are no chapters in that class so it looks like 2.3 TITLE.

The * form shows TITLE. But it does not show the section number, does not increment the section counter, and produces no table of contents entry.

The optional argument TOC-TITLE will appear as the section title in the table of contents (see Table of contents etc.).  If it is not present then TITLE will be there.  This shows the full name in the title of the section,

     \subsection[$\alpha,\beta,\gamma$ paper]{\textit{The Origin of
       Chemical Elements} by R.A.~Alpher, H.~Bethe, and G.~Gamow}

but only,,
paper on the contents page.

For determining which sectional units are numbered and which appear in the table of contents, the level number of a subsection is 2 (see Sectioning/secnumdepth and see Sectioning/tocdepth).

The paragraph that follows the subsection title is not indented, as is a standard typographical practice.  One way to get an indent is to use the package indentfirst.

There are a number of ways to change the behavior of the \subsection command.  One is the \@startsection command (see \@startsection).  There are also many packages on CTAN that address this, including titlesec.  See the documentation but the example below gives a sense of what they can do.

     \usepackage{titlesec}   % in preamble
     \titleformat{\subsection}[runin]
       {\normalfont\normalsize\bfseries}  % format of the title
       {\thesubsection}                   % label
       {0.6em}                            % space between label and title
       {}                                 % before-code hook

That puts the subsection number and TITLE in the first line of text.

\subsubsection, \paragraph, \subparagraph
=========================================

Synopsis, one of:

     \subsubsection{TITLE}
     \subsubsection*{TITLE}
     \subsubsection[TOC-TITLE]{TITLE}

or one of:

     \paragraph{TITLE}
     \paragraph*{TITLE}
     \paragraph[TOC-TITLE]{TITLE}

or one of:

     \subparagraph{TITLE}
     \subparagraph*{TITLE}
     \subparagraph[TOC-TITLE]{TITLE}

Start a subsubsection, paragraph, or subparagraph.  The standard LaTeX classes article, book, and report all have these commands, although they are not commonly used.

This produces a subsubsection.

     \subsubsection{Piston ring compressors: structural performance}
     Provide exterior/interior wall cladding assemblies
     capable of withstanding the effects of load and stresses from
     consumer-grade gasoline engine piston rings.

The default output of each of the three does not change over the standard LaTeX classes article, book, and report.  For \subsubsection the TITLE is alone on its line, in boldface and normal size type.  For \paragraph the TITLE is inline with the text, not indented, in boldface and normal size type.  For \subparagraph the TITLE is inline with the text, with a paragraph indent, in boldface and normal size type (Because an article has no chapters its subsubsections are numbered and so it looks like 1.2.3 TITLE, for section 1, subsection 2, and subsubsection 3.  The other two divisions are not numbered.)

The * form shows TITLE.  But it does not increment the associated counter and produces no table of contents entry (and does not show the number for \subsubsection).

The optional argument TOC-TITLE will appear as the division title in the table of contents (see Table of contents etc.).  If it is not present then TITLE will be there.

For determining which sectional units are numbered and which appear in the table of contents, the level number of a subsubsection is 3, of a paragraph is 4, and of a subparagraph is 5 (see Sectioning/secnumdepth and see Sectioning/tocdepth).

The paragraph that follows the subsubsection title is not indented, as is a standard typographical practice.  One way to get an indent is to use the package indentfirst.

There are a number of ways to change the behavior of the these commands. One is the \@startsection command (see \@startsection). There are also many packages on CTAN that address this, including titlesec.  See the documentation on CTAN.

\appendix
=========

Synopsis:

     \appendix

This does not directly produce any output.  But in a book or report it declares that subsequent \chapter commands start an appendix.  In an article it does the same, for \section commands.  It also resets the chapter and section counters to 0 in a book or report, and in an article resets the section and subsection counters.

In this book

     \chapter{One}  ...
     \chapter{Two}  ...
      ...
     \appendix
     \chapter{Three}  ...
     \chapter{Four}  ...

the first two will generate output numbered Chapter 1 and Chapter 2.  After the \appendix the numbering will be Appendix A and Appendix B.  See Larger book template for another example.

appendix The appendix package adds the command \appendixpage to put a separate Appendices in the document body before the first appendix, and the command \addappheadtotoc to do the same in the table of contents.  You can reset the name Appendix with a command like \renewcommand{\appendixname}{Specification}, as well as a number of other features.  See the documentation on CTAN.

\frontmatter, \mainmatter, \backmatter
======================================

Synopsis, one of:

     \frontmatter
     \mainmatter
     \backmatter

Format a book class document differently according to which part of the document is being produced.  All three commands are optional.

Traditionally, a book's front matter contains such things as the title page, an abstract, a table of contents, a preface, a list of notations, a list of figures, and a list of tables.  (Some of these front matter pages, such as the title page, are traditionally not numbered.)  The back matter may contain such things as a glossary, notes, a bibliography, and an index.

The \frontmatter declaration makes the pages numbered in lowercase roman, and makes chapters not numbered, although each chapter's title appears in the table of contents; if you use other sectioning commands here, use the *-version (see Sectioning). The \mainmatter changes the behavior back to the expected version, and resets the page number.  The \backmatter leaves the page numbering alone but switches the chapters back to being not numbered.  See Larger book template for an example using the three.

\@startsection
==============

Synopsis:

     \@startsection{NAME}{LEVEL}{INDENT}{BEFORESKIP}{AFTERSKIP}{STYLE}

Used to help redefine the behavior of commands that start sectioning divisions such as \section or \subsection.

Note that the titlesec package makes manipulation of sectioning easier.  Further, while most requirements for sectioning commands can be satisfied with \@startsection, some cannot.  For instance, in the standard LaTeX book and report classes the commands \chapter and \report are not constructed in this way.  To make such a command you may want to use the \secdef command.

Technically, \@startsection has the form

     \@startsection{NAME}
       {LEVEL}
       {INDENT}
       {BEFORESKIP}
       {AFTERSKIP}
       {STYLE}*[TOCTITLE]{TITLE}

so that issuing

     \renewcommand{\section}{\@startsection{NAME}
       {LEVEL}
       {INDENT}
       {BEFORESKIP}
       {AFTERSKIP}
       {STYLE}}

redefines \section to have the form \section*[TOCTITLE]{TITLE} (here too, the star * is optional).  See Sectioning.  This implies that when you write a command like \renewcommand{section}{...}, the \@startsection{...} must come last in the definition.  See the examples below.

name
     Name of the counter used to number the sectioning header.  This counter must be defined separately.  Most commonly this is either section, subsection, or paragraph.  Although in those cases the counter name is the same as the sectioning command itself, you don't have to use the same name.

     Then \theNAME displays the title number and \NAMEmark is for the page headers.  See the third example below.

level
     An integer giving the depth of the sectioning command. See Sectioning for the list of standard level numbers.

     If LEVEL is less than or equal to the value of the counter secnumdepth then titles for this sectioning command will be numbered (see Sectioning/secnumdepth).  For instance, if secnumdepth is 1 in an article then the command \section{Introduction} will produce output like ``1 Introduction'' while \subsection{Discussion} will produce output like ``Discussion'', without the number prefix.

     If LEVEL is less than or equal to the value of the counter TOCDEPTH then the table of contents will have an entry for this sectioning unit (see Sectioning/tocdepth).  For instance, in an article, if TOCDEPTH is 1 then the table of contents will list sections but not subsections.

indent
     A length giving the indentation of all of the title lines with respect to the left margin.  To have the title flush with the margin use 0pt.  A negative indentation such as -\parindent will move the title into the left margin.

beforeskip
     The absolute value of this length is the amount of vertical space that is inserted before this sectioning unit's title.  This space will be discarded if the sectioning unit happens to start at the top of a fresh page.  If this number is negative then the first paragraph following the header is not indented, if it is non-negative then the first paragraph is indented.  (Note that the negative of 1pt plus 2pt minus 3pt is -1pt plus -2pt minus -3pt.)

     For example, if BEFORESKIP is -3.5ex plus -1ex minus -0.2ex then to start the new sectioning unit, LaTeX will add about 3.5 times the height of a letter x in vertical space, and the first paragraph in the section will not be indented.  Using a rubber length, with plus and minus, is good practice here since it gives LaTeX more flexibility in making up the page (see Lengths).

     The full accounting of the vertical space between the baseline of the line prior to this sectioning unit's header and the baseline of the header is that it is the sum of the \parskip of the text font, the \baselineskip of the title font, and the absolute value of the BEFORESKIP.  This space is typically rubber so it may stretch or shrink.  (If the sectioning unit starts on a fresh page so that the vertical space is discarded then the baseline of the header text will be where LaTeX would put the baseline of the first text line on that page.)

afterskip
     This is a length.  If AFTERSKIP is non-negative then this is the vertical space inserted after the sectioning unit's title header.  If it is negative then the title header becomes a run-in header, so that it becomes part of the next paragraph.  In this case the absolute value of the length gives the horizontal space between the end of the title and the beginning of the following paragraph.  (Note that the negative of 1pt plus 2pt minus 3pt is -1pt plus -2pt minus -3pt.)

     As with BEFORESKIP, using a rubber length, with plus and minus components, is good practice here since it gives LaTeX more flexibility in putting together the page.

     If afterskip is non-negative then the full accounting of the vertical space between the baseline of the sectioning unit's header and the baseline of the first line of the following paragraph is that it is the sum of the \parskip of the title font, the \baselineskip of the text font, and the value of AFTER. That space is typically rubber so it may stretch or shrink.  (Note that because the sign of afterskip changes the sectioning unit header's from standalone to run-in, you cannot use a negative afterskip to cancel part of the \parskip.)

style
     Controls the styling of the title.  See the examples below.  Typical commands to use here are \centering, \raggedright, \normalfont, \hrule, or \newpage.  The last command in STYLE may be one that takes one argument, such as \MakeUppercase or \fbox that takes one argument.  The section title will be supplied as the argument to this command. For instance, setting STYLE to \bfseries\MakeUppercase would produce titles that are bold and uppercase.

These are LaTeX's defaults for the first three sectioning units that are defined with \@startsection, for the article, book, and report classes.  For section, the LEVEL is 1, the INDENT is 0pt, the BEFORESKIP is -3.5ex plus -1ex minus -0.2ex, the AFTERSKIP is 2.3ex plus 0.2ex, and the STYLE is \normalfont\Large\bfseries.  For subsection, the LEVEL is 2, the INDENT is 0pt, the BEFORESKIP is -3.25ex plus -1ex minus -0.2ex, the AFTERSKIP is 1.5ex plus 0.2ex, and the STYLE is \normalfont\large\bfseries.  For subsubsection, the LEVEL is 3, the INDENT is 0pt, the BEFORESKIP is -3.25ex plus -1ex minus -0.2ex, the AFTERSKIP is 1.5ex plus 0.2ex, and the STYLE is \normalfont\normalsize\bfseries.

Here are examples.  They go either in a package or class file or in the preamble of a LaTeX document.  If you put them in the preamble they must go between a \makeatletter command and a \makeatother.  (Probably the error message You can't use `\spacefactor' in vertical mode.  means that you forgot this.) See \makeatletter & \makeatother.

This will put section titles in large boldface type, centered.  It says \renewcommand because LaTeX's standard classes have already defined a \section.  For the same reason it does not define a section counter, or the commands \thesection and \l@section.

     \renewcommand\section{%
       \@startsection{section}% NAME
         {1}% LEVEL
         {0pt}% INDENT
         {-3.5ex plus -1ex minus -.2ex}% BEFORESKIP
         {2.3ex plus.2ex}% AFTERSKIP
         {\centering\normalfont\Large\bfseries}% STYLE
       }

This will put subsection titles in small caps type, inline with the paragraph.

     \renewcommand\subsection{%
       \@startsection{subsection}%  NAME
         {2}% LEVEL
         {0em}% INDENT
         {-1ex plus 0.1ex minus -0.05ex}% BEFORESKIP
         {-1em plus 0.2em}% AFTERSKIP
         {\scshape}% STYLE
       }

The prior examples redefined existing sectional unit title commands. This defines a new one, illustrating the needed counter and macros to display that counter.

     \setcounter{secnumdepth}{6}% show counters this far down
     \newcounter{subsubparagraph}[subparagraph]% counter for numbering
     \renewcommand{\thesubsubparagraph}%               how to display
       {\thesubparagraph.\@arabic\c@subsubparagraph}%  numbering
     \newcommand{\subsubparagraph}{\@startsection
                              {subsubparagraph}%
                              {6}%
                              {0em}%
                              {\baselineskip}%
                              {0.5\baselineskip}%
                              {\normalfont\normalsize}}
     \newcommand*\l@subsubparagraph{\@dottedtocline{6}{10em}{5em}}% for toc
     \newcommand{\subsubparagraphmark}[1]{}% for page headers

Cross references
****************

We often want something like See Theorem~31.  But by-hand typing the 31 is poor practice.  Instead you should write a label such as \label{eq:GreensThm} and then reference it, as with See equation~\ref{eq:GreensThm}.  LaTeX will automatically work out the number, put it into the output, and will change that number later if needed.

     We will see this with Theorem~\ref{th:GreensThm}. % forward reference
     ...
     \begin{theorem} \label{th:GreensThm}
       ...
     \end{theorem}
     ...
     See Theorem~\ref{th:GreensThm} on page~\pageref{th:GreensThm}.

LaTeX tracks cross reference information in a file having the extension .aux and with the same base name as the file containing the \label.  So if \label is in calculus.tex then the information is in calculus.aux.  LaTeX puts the information in that file every time it runs across a \label.

The behavior described in the prior paragraph results in a quirk that happens when your document has a forward reference, a \ref that appears before the associated \label.  If this is the first time that you are compiling the document then you will get LaTeX Warning: Label(s) may have changed. Rerun to get cross references right and in the output the forward reference will appear as two question marks ??, in boldface.  A similar thing happens if you change some things so the references changes; you get the same warning and the output contains the old reference information.  In both cases, resolve this by compiling the document a second time.

cleveref The cleveref package enhances LaTeX's cross referencing features.  You can arrange that if you enter \begin{thm}\label{th:Nerode}...\end{thm} then \cref{th:Nerode} will output Theorem 3.21, without you having to enter the ``Theorem.''

\label
======

Synopsis:

     \label{KEY}

Assign a reference number to KEY.  In ordinary text \label{KEY} assigns to KEY the number of the current sectional unit. Inside an environment with numbering, such as a table or theorem environment, \label{KEY} assigns to KEY the number of that environment.  Retrieve the assigned number with the \ref{KEY} command (see \ref).

A key name can consist of any sequence of letters, digits, or common punctuation characters.  Upper and lowercase letters are distinguished, as usual.

A common convention is to use labels consisting of a prefix and a suffix separated by a colon or period.  Thus, \label{fig:Post} is a label for a figure with a portrait of Emil Post.  This helps to avoid accidentally creating two labels with the same name, and makes your source more readable.  Some commonly-used prefixes:

ch
     for chapters

sec
subsec
     for lower-level sectioning commands

fig
     for figures

tab
     for tables

eq
     for equations

In the auxiliary file the reference information is kept as the text of a command of the form \newlabel{LABEL}{{CURRENTLABEL}{PAGENUMBER}}. Here CURRENTLABEL is the current value of the macro \@currentlabel that is usually updated whenever you call \refstepcounter{COUNTER}.

Below, the key sec:test will get the number of the current section and the key fig:test will get the number of the figure. (Incidentally, put labels after captions in figures and tables.)

     \section{section name}
     \label{sec:test}
     This is Section~\ref{sec:test}.
     \begin{figure}
       ...
       \caption{caption text}
       \label{fig:test}
     \end{figure}
     See Figure~\ref{fig:test}.

\pageref
========

Synopsis:

     \pageref{KEY}

Produce the page number of the place in the text where the corresponding \label{KEY} command appears.

If there is no \label{KEY} then you get something like LaTeX Warning: Reference `th:GrensThm' on page 1 undefined on input line 11.

Below, the \label{eq:main} is used both for the formula number and for the page number.  (Note that the two references are forward references so this document would need to be compiled twice to resolve those.)

     The main result is formula~\ref{eq:main} on page~\pageref{eq:main}.
       ...
     \begin{equation} \label{eq:main}
        \mathbf{P}=\mathbf{NP}
     \end{equation}

\ref
====

Synopsis:

     \ref{KEY}

Produces the number of the sectional unit, equation, footnote, figure, ..., of the corresponding \label command (see \label).  It does not produce any text, such as the word `Section' or `Figure', just the bare number itself.

If there is no \label{KEY} then you get something like LaTeX Warning: Reference `th:GrensThm' on page 1 undefined on input line 11.

In this example the \ref{popular} produces 2.  Note that it is a forward reference since it comes before \label{popular} so this document would have to be compiled twice.

     The most widely-used format is item number~\ref{popular}.
     \begin{enumerate}
     \item Plain \TeX
     \item \label{popular} \LaTeX
     \item Con\TeX t
     \end{enumerate}

The cleveref package includes text such as Theorem in the reference.  See the documentation on CTAN.

Environments
************

LaTeX provides many environments for delimiting certain behavior. An environment begins with \begin and ends with \end, like this:

     \begin{ENVIRONMENT-NAME}
       ...
     \end{ENVIRONMENT-NAME}

The ENVIRONMENT-NAME at the beginning must exactly match that at the end. For instance, the input \begin{table*}...\end{table} will cause an error like: ! LaTeX Error: \begin{table*} on input line 5 ended by \end{table}.

Environments are executed within a group.

abstract
========

Synopsis:

     \begin{abstract}
     ...
     \end{abstract}

Produce an abstract, possibly of multiple paragraphs.  This environment is only defined in the article and report document classes (see Document classes).

Using the example below in the article class produces a displayed paragraph.  Document class option titlepage causes the abstract to be on a separate page (see Document class options); this is the default only in the report class.

     \begin{abstract}
       We compare all known accounts of the proposal made by Porter Alexander
       to Robert E Lee at the Appomattox Court House that the army continue
       in a guerrilla war, which Lee refused.
     \end{abstract}

The next example produces a one column abstract in a two column document (for a more flexible solution, use the package abstract).

     \documentclass[twocolumn]{article}
       ...
     \begin{document}
     \title{Babe Ruth as Cultural Progenitor: a Atavistic Approach}
     \author{Smith \\ Jones \\ Robinson\thanks{Railroad tracking grant.}}
     \twocolumn[
       \begin{@twocolumnfalse}
          \maketitle
          \begin{abstract}
            Ruth was not just the Sultan of Swat, he was the entire swat
            team.
          \end{abstract}
        \end{@twocolumnfalse}
        ]
     {   % by-hand insert a footnote at page bottom
      \renewcommand{\thefootnote}{\fnsymbol{footnote}}
      \footnotetext[1]{Thanks for all the fish.}
     }

array
=====

Synopsis:

     \begin{array}{COLS}
       COLUMN 1 ENTRY &COLUMN 2 ENTRY ... &COLUMN N ENTRY \\
       ...
     \end{array}

or:

     \begin{array}[POS]{COLS}
       COLUMN 1 ENTRY &COLUMN 2 ENTRY ... &COLUMN N ENTRY \\
       ...
     \end{array}

Produce a mathematical array.  This environment can only be used in math mode, and normally appears within a displayed mathematics environment such as equation (see equation).  Inside of each row the column entries are separated by an ampersand, (&).  Rows are terminated with double-backslashes (see \\).

This example shows a three by three array.

     \begin{equation*}
       \chi(x) =
       \left|              % vertical bar fence
         \begin{array}{ccc}
           x-a  &-b  &-c  \\
           -d   &x-e &-f  \\
           -g   &-h  &x-i
         \end{array}
      \right|
     \end{equation*}

The required argument COLS describes the number of columns, their alignment, and the formatting of the intercolumn regions.  For instance, \begin{array}{rcl}...\end{array} gives three columns: the first flush right, the second centered, and the third flush left.  See tabular for the complete description of COLS and of the other common features of the two environments, including the optional POS argument.

There are two ways that array diverges from tabular.  The first is that array entries are typeset in math mode, in textstyle (see Modes) except if the COLS definition specifies the column with p{...}, which causes the entry to be typeset in text mode.  The second is that, instead of tabular's parameter \tabcolsep, LaTeX's intercolumn space in an array is governed by \arraycolsep, which gives half the width between columns. The default for this is 5pt so that between two columns comes 10pt of space.

To obtain arrays with braces the standard is to use the amsmath package.  It comes with environments pmatrix for an array surrounded by parentheses (...), bmatrix for an array surrounded by square brackets [...], Bmatrix for an array surrounded by curly braces {...}, vmatrix for an array surrounded by vertical bars |...|, and Vmatrix for an array surrounded by double vertical bars ||...||, along with a number of other array constructs.

The next example uses the amsmath package.

     \usepackage{amsmath}  % in preamble

     \begin{equation}
       \begin{vmatrix}{cc}  % array with vert lines
         a  &b \\
         c  &d
       \end{vmatrix}=ad-bc
     \end{equation}

There are many packages concerning arrays.  The array package has many useful extensions, including more column types.  The dcolumn package adds a column type to center on a decimal point.  For both see the documentation on CTAN.

center
======

Synopsis:

     \begin{center}
       LINE1 \\
       LINE2 \\
       ...
     \end{center}

Create a new paragraph consisting of a sequence of lines that are centered within the left and right margins.  Use double-backslash, \\, to get a line break (see \\). If some text is too long to fit on a line then LaTeX will insert line breaks that avoid hyphenation and avoid stretching or shrinking any interword space.

This environment inserts space above and below the text body.  See \centering to avoid such space, for example inside a figure environment.

This example produces three centered lines.  There is extra vertical space between the last two lines.

     \begin{center}
       A Thesis Submitted in Partial Fufillment \\
       of the Requirements of \\[0.5ex]
       the School of Environmental Engineering
     \end{center}

In this example, depending on the page's line width, LaTeX may choose a line break for the part before the double backslash.  If so, it will center each of the two lines and if not it will center the single line. Then LaTeX will break at the double backslash, and will center the ending.

     \begin{center}
       My father considered that anyone who went to chapel and didn't drink
       alcohol was not to be tolerated.\\
       I grew up in that belief.  --Richard Burton
     \end{center}

A double backslash after the final line is optional.  If present it doesn't add any vertical space.

In a two-column document the text is centered in a column, not in the entire page.

\centering
----------

Synopsis:

     {\centering ... }

or

     \begin{group}
       \centering ...
     \end{group}

Center the material in its scope.  It is most often used inside an environment such as figure, or in a parbox.

This example's \centering declaration causes the graphic to be horizontally centered.

     \begin{figure}
       \centering
       \includegraphics[width=0.6\textwidth]{ctan_lion.png}
       \caption{CTAN Lion}  \label{fig:CTANLion}
     \end{figure}

The scope of this \centering ends with the \end{figure}.

Unlike the center environment, the \centering command does not add vertical space above and below the text.  That's its advantage in the above example; there is not an excess of space.

It also does not start a new paragraph; it simply changes how LaTeX formats paragraph units.  If ww {\centering xx \\ yy} zz is surrounded by blank lines then LaTeX will create a paragraph whose first line ww xx is centered and whose second line, not centered, contains yy zz.  Usually what is desired is for the scope of the declaration to contain a blank line or the \end command of an environment such as figure or table that ends the paragraph unit.  Thus, if {\centering xx \\ yy\par} zz is surrounded by blank lines then it makes a new paragraph with two centered lines xx and yy, followed by a new paragraph with zz that is formatted as usual.

description
===========

Synopsis:

     \begin{description}
       \item[LABEL OF FIRST ITEM] TEXT OF FIRST ITEM
       \item[LABEL OF SECOND ITEM] TEXT OF SECOND ITEM
        ...
     \end{description}

Environment to make a list of labeled items.  Each item's LABEL is typeset in bold and is flush left, so that long labels continue into the first line of the item text.  There must be at least one item; having none causes the LaTeX error Something's wrong--perhaps a missing \item.

This example shows the environment used for a sequence of definitions.

     \begin{definition}
       \item[lama] A priest.
       \item[llama] A beast.
     \end{definition}

The labels lama and llama are output in boldface, with the left edge on the left margin.

Start list items with the \item command (see \item).  Use the optional labels, as in \item[Main point], because there is no sensible default.  Following the \item is optional text, which may contain multiple paragraphs.

Since the labels are in bold style, if the label text calls for a font change given in argument style (see Font styles) then it will come out bold.  For instance, if the label text calls for typewriter with \item[\texttt{label text}] then it will appear in bold typewriter, if that is available. The simplest way around this, in this example to get non-bold typewriter, is to use declarative style: \item[{\tt label text}].  Similarly, get the standard roman font with \item[{\rm label text}].

For other major LaTeX labelled list environments, see itemize and enumerate.  Unlike those environments, nesting description environments does not change the default label; it is boldface and flush left at all levels.

For information about list layout parameters, including the default values, and for information about customizing list layout, see list.  The package enumitem is useful for customizing lists.

This example changes the description labels to small caps.

     \renewcommand{\descriptionlabel}[1]{%
       {\hspace{\labelsep}\textsc{#1}}}

displaymath
===========

Synopsis:

     \begin{displaymath}
       MATHEMATICAL TEXT
     \end{displaymath}

Environment to typeset the math text on its own line, in display style and centered.  To make the text be flush-left use the global option fleqn; see Document class options.

In the displaymath environment no equation number is added to the math text. One way to get an equation number is to use the equation environment (see equation).

LaTeX will not break the MATH TEXT across lines.

Note that the amsmath package has significantly more extensive displayed equation facilities.  For example, there are a number of ways in that package for having math text broken across lines.

The construct \[MATH TEXT\] is essentially a synonym for \begin{displaymath}MATH TEXT\end{displaymath} but the latter is easier to work with in the source file; for instance, searching for a square bracket may get false positives but the word displaymath will likely be unique.  (The construct $$MATH TEXT$$ from Plain TeX is sometimes mistakenly used as a synonym for displaymath.  It is not a synonym, because the displaymath environment checks that it isn't started in math mode and that it ends in math mode begun by the matching environment start, because the displaymath environment has different vertical spacing, and because the displaymath environment honors the fleqn option.)

The output from this example is centered and alone on its line.

     \begin{displaymath}
       \int_1^2 x^2\,dx=7/3
     \end{displaymath}

Also, the integral sign is larger than the inline version \( \int_1^2 x^2\,dx=7/3 \) produces.

document
========

The document environment encloses the entire body of a document. It is required in every LaTeX document.  See Starting and ending.

\AtBeginDocument
----------------

Synopsis:

     \AtBeginDocument{CODE}

Save CODE and execute it when \begin{document} is executed, at the very end of the preamble.  The code is executed after the font selection tables have been set up, so the normal font for the document is the current font.  However, the code is executed as part of the preamble so you cannot do any typesetting with it.

You can issue this command more than once; the successive code lines will be executed in the order that you gave them.

\AtEndDocument
--------------

Synopsis:

     \AtEndDocument{CODE}

Save CODE and execute it near the end of the document. Specifically, it is executed when \end{document} is executed, before the final page is finished and before any leftover floating environments are processed. If you want some of the code to be executed after these two processes then include a \clearpage at the appropriate point in CODE.

You can issue this command more than once; the successive code lines will be executed in the order that you gave them.

enumerate
=========

Synopsis:

     \begin{enumerate}
       \item[OPTIONAL LABEL OF FIRST ITEM] TEXT OF FIRST ITEM
       \item[OPTIONAL LABEL OF SECOND ITEM] TEXT OF SECOND ITEM
       ...
     \end{enumerate}

Environment to produce a numbered list of items.  The format of the label numbering depends on the nesting level of this environment; see below. The default top-level numbering is 1., 2., etc. Each enumerate list environment must have at least one item; having none causes the LaTeX error Something's wrong--perhaps a missing \item.

This example gives the first two finishers in the 1908 Olympic marathon. As a top-level list the labels would come out as 1. and 2..

     \begin{enumerate}
      \item Johnny Hayes (USA)
      \item Charles Hefferon (RSA)
     \end{enumerate}

Start list items with the \item command (see \item).  If you give \item an optional argument by following it with square brackets, as in \item[Interstitial label], then the next item will continue the interrupted sequence (see \item).  That is, you will get labels like 1., then Interstitial label, then 2..  Following the \item is optional text, which may contain multiple paragraphs.

Enumerations may be nested within other enumerate environments, or within any paragraph-making environment such as itemize (see itemize), up to four levels deep.  This gives LaTeX's default for the format at each nesting level, where 1 is the top level, the outermost level.

 1. arabic number followed by a period: 1., 2., ...

 2. lowercase letter inside parentheses: (a), (b) ...

 3. lowercase roman numeral followed by a period: i., ii., ...

 4. uppercase letter followed by a period: A., B., ...

The enumerate environment uses the counters \enumi through \enumiv (see Counters).

For other major LaTeX labeled list environments, see description and itemize.  For information about list layout parameters, including the default values, and for information about customizing list layout, see list.  The package enumitem is useful for customizing lists.

To change the format of the label use \renewcommand (see \newcommand & \renewcommand) on the commands \labelenumi through \labelenumiv. For instance, this first level list will be labelled with uppercase letters, in boldface, and without a trailing period.

     \renewcommand{\labelenumi}{\textbf{\Alph{enumi}}}
     \begin{enumerate}
       \item Shows as boldface A
       \item Shows as boldface B
     \end{enumerate}

For a list of counter-labeling commands see \alph \Alph \arabic \roman \Roman \fnsymbol.

eqnarray
========

The eqnarray environment is obsolete.  It has infelicities, including spacing that is inconsistent with other mathematics elements. (See ``Avoid eqnarray!'' by Lars Madsen http://tug.org/TUGboat/tb33-1/tb103madsen.pdf).  New documents should include the amsmath package and use the displayed mathematics environments provided there, such as the align environment.  We include a description only for completeness and for working with old documents.

Synopsis:

     \begin{eqnarray}
       FIRST FORMULA LEFT  &FIRST FORMULA MIDDLE  &FIRST FORMULA RIGHT \\
       ...
     \end{eqnarray}

or

     \begin{eqnarray*}
       FIRST FORMULA LEFT  &FIRST FORMULA MIDDLE  &FIRST FORMULA RIGHT \\
       ...
     \end{eqnarray*}

Display a sequence of equations or inequalities.  The left and right sides are typeset in display mode, while the middle is typeset in text mode.

It is similar to a three-column array environment, with items within a row separated by an ampersand (&), and with rows separated by double backslash  \\). The starred form of line break (\\*) can also be used to separate equations, and will disallow a page break there (see \\).

The unstarred form eqnarray places an equation number on every line (using the equation counter), unless that line contains a \nonumber command.  The starred form eqnarray* omits equation numbering, while otherwise being the same.

The command \lefteqn is used for splitting long formulas across lines. It typesets its argument in display style flush left in a box of zero width.

This example shows three lines.  The first two lines make an inequality, while the third line has not entry on the left side.

     \begin{eqnarray*}
       \lefteqn{x_1+x_2+\cdots+x_n}     \\
         &\leq &y_1+y_2+\cdots+y_n      \\
         &=    &z+y_3+\cdots+y_n
     \end{eqnarray*}

equation
========

Synopsis:

     \begin{equation}
       MATHEMATICAL TEXT
     \end{equation}

The same as a displaymath environment (see displaymath) except that LaTeX puts an equation number flush to the right margin. The equation number is generated using the equation counter.

You should have no blank lines between \begin{equation} and \begin{equation}, or LaTeX will tell you that there is a missing dollar sign.

The package amsmath package has extensive displayed equation facilities.  New documents should include this package.

figure
======

Synopsis:

     \begin{figure}[PLACEMENT]
       FIGURE BODY
       \caption[LOFTITLE]{TITLE}  % optional
       \label{LABEL}              % optional
     \end{figure}

or:

     \begin{figure*}[PLACEMENT]
       FIGURE BODY
       \caption[LOFTITLE]{TITLE}  % optional
       \label{LABEL}              % optional
     \end{figure*}

Figures are for material that is not part of the normal text.  An example is material that you cannot have split between two pages, such as a graphic.  Because of this, LaTeX does not typeset figures in sequence with normal text but instead ``floats'' them to a convenient place, such as the top of a following page (see Floats).

The FIGURE BODY can consist of imported graphics (see Graphics), or text, LaTeX commands, etc.  It is typeset in a parbox of width \textwidth.

The possible values of PLACEMENT are h for here, t for top, b for bottom, and p for on a separate page of floats.  For the effect of these options on the float placement algorithm, see Floats.

The starred form figure* is used when a document is in double-column mode (see \twocolumn).  It produces a figure that spans both columns, at the top of the page.  To add the possibility of placing at a page bottom see the discussion of PLACEMENT b in Floats.

The label is optional; it is used for cross references (see Cross references). The optional \caption command specifies caption text for the figure.  By default it is numbered.  If LOFTITLE is present, it is used in the list of figures instead of TITLE (see Table of contents etc.).

This example makes a figure out of a graphic.  LaTeX will place that graphic and its caption at the top of a page or, if it is pushed to the end of the document, on a page of floats.

     \usepackage{graphicx}  % in preamble
       ...
     \begin{figure}[t]
       \centering
       \includegraphics[width=0.5\textwidth]{CTANlion.png}
       \caption{The CTAN lion, by Duane Bibby}
     \end{figure}

filecontents: Write an external file
====================================

Synopsis:

     \begin{filecontents}{FILENAME}
       TEXT
     \end{filecontents}

or

     \begin{filecontents*}{FILENAME}
       TEXT
     \end{filecontents*}

Create a file named FILENAME and fill it with TEXT.  The unstarred version of the environment filecontents prefixes the content of the created file with a header; see the example below.  The starred version filecontents* does not include the header.

This environment can be used anywhere in the preamble, although it often appears before the \documentclass command.  It is typically used when a source file requires a nonstandard style or class file.  The environment will write that file to the directory containing the source and thus make the source file self-contained.  Another use is to include bib references in the file, again to make it self-contained.

The environment checks whether a file of that name already exists and if so, does not do anything.  There is a filecontents package that redefines the filecontents environment so that instead of doing nothing in that case, it will overwrite the existing file.

For example, this document

     \documentclass{article}
     \begin{filecontents}{JH.sty}
     \newcommand{\myname}{Jim Hef{}feron}
     \end{filecontents}
     \usepackage{JH}
     \begin{document}
     Article by \myname.
     \end{document}

produces this file JH.sty.

     %% LaTeX2e file `JH.sty'
     %% generated by the `filecontents' environment
     %% from source `test' on 2015/10/12.
     %%
     \newcommand{\myname}{Jim Hef{}feron}

flushleft
=========

Synopsis:

     \begin{flushleft}
       LINE1 \\
       LINE2 \\
       ...
     \end{flushleft}

An environment that creates a paragraph whose lines are flush to the left-hand margin, and ragged right. If you have lines that are too long then LaTeX will linebreak them in a way that avoids hyphenation and stretching or shrinking spaces.  To force a new line use a double backslash, \\.  For the declaration form see \raggedright.

This creates a box of text that is at most 3 inches wide, with the text flush left and ragged right.

     \noindent\begin{minipage}{3in}
     \begin{flushleft}
       A long sentence that will be broken by \LaTeX{}
         at a convenient spot. \\
       And, a fresh line forced by the double backslash.
     \end{flushleft}
     \end{minipage}

\raggedright
------------

Synopses:

     {\raggedright  ... }

or

     \begin{ENVIRONMENT} \raggedright
       ...
     \end{ENVIRONMENT}

A declaration which causes lines to be flush to the left margin and ragged right. It can be used inside an environment such as quote or in a parbox.  For the environment form see flushleft.

Unlike the flushleft environment, the \raggedright command does not start a new paragraph; it only changes how LaTeX formats paragraph units.  To affect a paragraph unit's format, the scope of the declaration must contain the blank line or \end command that ends the paragraph unit.

Here \raggedright in each second column keeps LaTeX from doing very awkward typesetting to fit the text into the narrow column.  Note that \raggedright is inside the curly braces {...} to delimit its effect.

     \begin{tabular}{rp{2in}}
       Team alpha  &{\raggedright This team does all the real work.} \\
       Team beta   &{\raggedright This team ensures that the water
                     cooler is never empty.}                         \\
     \end{tabular}

flushright
==========

     \begin{flushright}
       LINE1 \\
       LINE2 \\
       ...
     \end{flushright}

An environment that creates a paragraph whose lines are flush to the right-hand margin and ragged left. If you have lines that are too long to fit the margins then LaTeX will linebreak them in a way that avoids hyphenation and stretching or shrinking spaces.  To force a new line use a double backslash, \\.  For the declaration form see \raggedleft.

For an example related to this environment, see flushleft.

\raggedleft
-----------

Synopses:

     {\raggedleft  ... }

or

     \begin{ENVIRONMENT} \raggedleft
       ...
     \end{ENVIRONMENT}

A declaration which causes lines to be flush to the right margin and ragged left. It can be used inside an environment such as quote or in a parbox.  For the environment form see flushright.

Unlike the flushright environment, the \raggedleft command does not start a new paragraph; it only changes how LaTeX formats paragraph units.  To affect a paragraph unit's format, the scope of the declaration must contain the blank line or \end command that ends the paragraph unit.

For an example related to this environment, see \raggedright.

itemize
=======

Synopsis:

     \begin{itemize}
       \item[OPTIONAL LABEL OF FIRST ITEM] TEXT OF FIRST ITEM
       \item[OPTIONAL LABEL OF SECOND ITEM] TEXT OF SECOND ITEM
       ...
     \end{itemize}

Produce a list that is unordered, sometimes called a bullet list.  The environment must have at least one \item; having none causes the LaTeX error Something's wrong--perhaps a missing \item.

This gives a two-item list.

     \begin{itemize}
      \item Pencil and watercolor sketch by Cassandra
      \item Rice portrait
     \end{itemize}

As a top-level list each label would come out as a bullet, *. The format of the labeling depends on the nesting level; see below.

Start list items with the \item command (see \item).  If you give \item an optional argument by following it with square brackets, as in \item[Optional label], then by default it will appear in bold and be flush right, so it could extend into the left margin.  For labels that are flush left see the description environment. Following the \item is optional text, which may contain multiple paragraphs.

Itemized lists can be nested within one another, up to four levels deep. They can also be nested within other paragraph-making environments, such as enumerate (see enumerate).  The itemize environment uses the commands \labelitemi through \labelitemiv to produce the default label (this also uses the convention of lowercase roman numerals at the end of the command names that signify the nesting level).  These are the default marks at each level.

 1. * (bullet, from \textbullet)

 2. -- (bold en-dash, from \normalfont\bfseries\textendash)

 3. * (asterisk, from \textasteriskcentered)

 4. . (centered dot, rendered here as a period, from \textperiodcentered)

Change the labels with \renewcommand.  For instance, this makes the first level use diamonds.

     \renewcommand{\labelitemi}{$\diamond$}

The distance between the left margin of the enclosing environment and the left margin of the itemize list is determined by the parameters \leftmargini through \leftmarginvi.  (Note the convention of using lowercase roman numerals a the end of the command name to denote the nesting level.)  The defaults are: 2.5em in level 1 (2em in two-column mode), 2.2em in level 2, 1.87em in level 3, and 1.7em in level 4, with smaller values for more deeply nested levels.

For other major LaTeX labeled list environments, see description and enumerate.  For information about list layout parameters, including the default values, and for information about customizing list layout, see list.  The package enumitem is useful for customizing lists.

This example greatly reduces the margin space for outermost itemized lists.

     \setlength{\leftmargini}{1.25em} % default 2.5em

Especially for lists with short items, it may be desirable to elide space between items.  Here is an example defining an itemize* environment with no extra spacing between items, or between paragraphs within a single item (\parskip is not list-specific, see \parindent & \parskip):

     \newenvironment{itemize*}%
       {\begin{itemize}%
         \setlength{\itemsep}{0pt}%
         \setlength{\parsep}{0pt}}%
         \setlength{\parskip}{0pt}}%
       {\end{itemize}}

letter environment: writing letters
===================================

This environment is used for creating letters.  See Letters.

list
====

Synopsis:

     \begin{list}{LABELING}{SPACING}
       \item[OPTIONAL LABEL OF FIRST ITEM] TEXT OF FIRST ITEM
       \item[OPTIONAL LABEL OF SECOND ITEM] TEXT OF SECOND ITEM
       ...
     \end{list}

An environment for constructing lists.

Note that this environment does not typically appear in the document body.  Most lists created by LaTeX authors are the ones that come standard: the description, enumerate, and itemize environments (see description, enumerate, and itemize).

Instead, the list environment is most often used in macros.  For example, many standard LaTeX environments that do not immediately appear to be lists are in fact constructed using list, including quotation, quote, and center (see quotation & quote, see center).

This uses the list environment to define a new custom environment.

     \newcounter{namedlistcounter}  % number the items
     \newenvironment{named}
       {\begin{list}
          {Item~\Roman{namedlistcounter}.} % labeling
          {\usecounter{namedlistcounter}   % set counter
           \setlength{\leftmargin}{3.5em}} % set spacing
       }
       {\end{list}}

     \begin{named}
       \item Shows as ``Item~I.''
       \item[Special label.] Shows as ``Special label.''
       \item Shows as ``Item~II.''
     \end{named}

The mandatory first argument LABELING specifies the default labeling of list items.  It can contain text and LaTeX commands, as above where it contains both Item and \Roman{...}. LaTeX forms the label by putting the LABELING argument in a box of width \labelwidth.  If the label is wider than that, the additional material extends to the right.  When making an instance of a list you can override the default labeling by giving \item an optional argument by including square braces and the text, as in the above \item[Special label.]; see \item.

The mandatory second argument SPACING has a list of commands. This list can be empty.  A command that can go in here is \usecounter{COUNTERNAME} (see \usecounter).  Use this to tell LaTeX to number the items using the given counter.  The counter will be reset to zero each time LaTeX enters the environment, and the counter is incremented by one each time LaTeX encounters an \item that does not have an optional argument.

 Another command that can go in SPACING is \makelabel, which constructs the label box.  By default it puts the contents flush right.  Its only argument is the label, which it typesets in LR mode (see Modes). One example of changing its definition is that to the above named example, before the definition of the environment add \newcommand{\namedmakelabel}[1]{\textsc{#1}}, and between the \setlength command and the parenthesis that closes the SPACING argument also add \let\makelabel\namedmakelabel. Then the items will be typeset in small caps.  Similarly, changing the second code line to \let\makelabel\fbox puts the labels inside a framed box.  Another example of the \makelabel command is below, in the definition of the redlabel environment.

Also often in SPACING are commands to redefine the spacing for the list.  Below are the spacing parameters with their default values. (Default values for derived environments such as itemize can be different than the values shown here.) See also the figure that follows the list.  Each is a length (see Lengths).  The vertical spaces are normally rubber lengths, with plus and minus components, to give TeX flexibility in setting the page.  Change each with a command such as \setlength{itemsep}{2pt plus1pt minus1pt}. For some effects these lengths should be zero or negative.

\itemindent
     Extra horizontal space indentation, beyond leftmargin, of the first line each item.  Its default value is 0pt.

\itemsep
     Vertical space between items, beyond the \parsep.  The defaults for the first three levels in LaTeX's article, book, and report classes at 10 point size are: 4pt plus2pt minus1pt, \parsep (that is, 2pt plus1pt minus1pt), and \topsep (that is, 2pt plus1pt minus1pt).  The defaults at 11 point are: 4.5pt plus2pt minus1pt, \parsep (that is, 2pt plus1pt minus1pt), and topsep (that is, 2pt plus1pt minus1pt).  The defaults at 12 point are: 5pt plus2.5pt minus1pt, \parsep (that is, 2.5pt plus1pt minus1pt), and \topsep (that is, 2.5pt plus1pt minus1pt).

\labelsep
     Horizontal space between the label and text of an item. The default for LaTeX's article, book, and report classes is 0.5em.

\labelwidth
     Horizontal width.  The box containing the label is nominally this wide. If \makelabel returns text that is wider than this then the first line of the item will be indented to make room for this extra material. If \makelabel returns text of width less than or equal to \labelwidth then LaTeX's default is that the label is typeset flush right in a box of this width.

     The left edge of the label box is \leftmargin+\itemindent-\labelsep-\labelwidth from the left margin of the enclosing environment.

     The default for LaTeX's article, book, and report classes at the top level is \leftmargini-\labelsep, (which is 2em in one column mode and 1.5em in two column mode).  At the second level it is \leftmarginii-\labelsep, and at the third level it is \leftmarginiii-\labelsep.  These definitions make the label's left edge coincide with the left margin of the enclosing environment.

\leftmargin
     Horizontal space between the left margin of the enclosing environment (or the left margin of the page if this is a top-level list), and the left margin of this list.  It must be non-negative.

     In the standard LaTeX document classes, a top-level list has this set to the value of \leftmargini, while a list that is nested inside a top-level list has this margin set to \leftmarginii.  More deeply nested lists get the values of \leftmarginiii through \leftmarginvi.  (Nesting greater than level five generates the error message Too deeply nested.)

     The defaults for the first three levels in LaTeX's article, book, and report classes are: \leftmargini is 2.5em (in two column mode, 2em), \leftmarginii is 2.2em, and \leftmarginiii is 1.87em.

\listparindent
     Horizontal space of additional line indentation, beyond \leftmargin, for second and subsequent paragraphs within a list item.  A negative value makes this an ``outdent''.  Its default value is 0pt.

\parsep
     Vertical space between paragraphs within an item.  In the book and article classes The defaults for the first three levels in LaTeX's article, book, and report classes at 10 point size are: 4pt plus2pt minus1pt, 2pt plus1pt minus1pt, and 0pt.  The defaults at 11 point size are: 4.5pt plus2pt minus1pt, 2pt plus1pt minus1pt, and 0pt.  The defaults at 12 point size are: 5pt plus2.5pt minus1pt, 2.5pt plus1pt minus1pt, and 0pt.

\partopsep
     Vertical space added, beyond \topsep+\parskip, to the top and bottom of the entire environment if the list instance is preceded by a blank line.  (A blank line in the LaTeX source before the list changes spacing at both the top and bottom of the list; whether the line following the list is blank does not matter.)

     The defaults for the first three levels in LaTeX's article, book, and report classes at 10 point size are: 2pt plus1 minus1pt, 2pt plus1pt minus1pt, and 1pt plus0pt minus1pt.  The defaults at 11 point are: 3pt plus1pt minus1pt, 3pt plus1pt minus1pt, and 1pt plus0pt minus1pt).  The defaults at 12 point are: 3pt plus2pt minus3pt, 3pt plus2pt minus2pt, and 1pt plus0pt minus1pt.

\rightmargin
     Horizontal space between the right margin of the list and the right margin of the enclosing environment.  Its default value is 0pt. It must be non-negative.

\topsep
     Vertical space added to both the top and bottom of the list, in addition to \parskip (see \parindent & \parskip).  The defaults for the first three levels in LaTeX's article, book, and report classes at 10 point size are: 8pt plus2pt minus4pt, 4pt plus2pt minus1pt, and 2pt plus1pt minus1pt.  The defaults at 11 point are: 9pt plus3pt minus5pt, 4.5pt plus2pt minus1pt, and 2pt plus1pt minus1pt.  The defaults at 12 point are: 10pt plus4pt minus6pt, 5pt plus2.5pt minus1pt, and 2.5pt plus1pt minus1pt.

This shows the horizontal and vertical distances.

The lengths shown are listed below.  The key relationship is that the right edge of the bracket for H1 equals the right edge of the bracket for H4, so that the left edge of the label box is at H3+H4-(H0+H1).

v0
     \topsep + \parskip if the list environment does not start a new paragraph, and \topsep+\parskip+\partopsep if it does

v1
     \parsep

v2
     \itemsep+\parsep

v3
     Same as V0.  (This space is affected by whether a blank line appears in the source above the environment; whether a blank line appears in the source below the environment does not matter.)

h0
     \labelwidth

h1
     \labelsep

h2
     \listparindent

h3
     \leftmargin

h4
     \itemindent

h5
     \rightmargin

The list's left and right margins, shown above as H3 and H5, are with respect to the ones provided by the surrounding environment, or with respect to the page margins for a top-level list.  The line width used for typesetting the list items is \linewidth (see Page layout parameters).  For instance, set the list's left margin to be one quarter of the distance between the left and right margins of the enclosing environment with \setlength{\leftmargin}{0.25\linewidth}.

Page breaking in a list structure is controlled by the three parameters below. For each, the LaTeX default is -\@lowpenalty, that is, -51.  Because it is negative, it somewhat encourages a page break at each spot.  Change it with, e.g., \@beginparpenalty=9999; a value of 10000 prohibits a page break.

\@beginparpenalty
     The page breaking penalty for breaking before the list (default -51).

\@itempenalty
     The page breaking penalty for breaking before a list item (default -51).

\@endparpenalty
     The page breaking penalty for breaking after a list (default -51).

The package enumitem is useful for customizing lists.

This example has the labels in red.  They are numbered, and the left edge of the label lines up with the left edge of the item text. See \usecounter.

     \usepackage{color}
     \newcounter{cnt}
     \newcommand{\makeredlabel}[1]{\textcolor{red}{#1.}}
     \newenvironment{redlabel}
       {\begin{list}
         {\arabic{cnt}}
         {\usecounter{cnt}
          \setlength{\labelwidth}{0em}
          \setlength{\labelsep}{0.5em}
          \setlength{\leftmargin}{1.5em}
          \setlength{\itemindent}{0.5em} % equals \labelwidth+\labelsep
          \let\makelabel=\makeredlabel
         }
       }
     {\end{list} }

\item: An entry in a list
-------------------------

Synopsis:

     \item text of item

or

     \item[OPTIONAL-LABEL] text of item

An entry in a list.  The entries are prefixed by a label, whose default depends on the list type.

Because the optional label is surrounded by square brackets [...], if you have an item whose text starts with [, you have to hide the bracket inside curly braces, as in: \item {[} is an open square bracket; otherwise, LaTeX will think it marks the start of an optional label.

Similarly, if the item does have the optional label and you need a close square bracket inside that label, you must hide it in the same way: \item[Close square bracket, {]}].  See LaTeX command syntax.

In this example the enumerate list has two items that use the default label and one that uses the optional label.

     \begin{enumerate}
       \item Moe
       \item[sometimes] Shemp
       \item Larry
     \end{enumerate}

The first item is labelled 1., the second item is labelled sometimes, and the third item is labelled 2..  Because of the optional label in the second item, the third item is not labelled 3..

trivlist: A restricted form of list
-----------------------------------

Synopsis:

     \begin{trivlist}
       ...
     \end{trivlist}

A restricted version of the list environment, in which margins are not indented and an \item without an optional argument produces no text.  It is most often used in macros, to define an environment where the \item command as part of the environment's definition.  For instance, the center environment is defined essentially like this:

     \newenvironment{center}
       {\begin{trivlist}\centering\item\relax}
       {\end{trivlist}}

Using trivlist in this way allows the macro to inherit some common code: combining vertical space of two adjacent environments; detecting whether the text following the environment should be considered a new paragraph or a continuation of the previous one; adjusting the left and right margins for possible nested list environments.

Specifically, trivlist uses the current values of the list parameters (see list), except that \parsep is set to the value of \parskip, and \leftmargin, \labelwidth, and \itemindent are set to zero.

This example outputs the items as two paragraphs, except that (by default) they have no paragraph indent and are vertically separated.

     \begin{trivlist}
     \item The \textit{Surprise} is not old; no one would call her old.
     \item She has a bluff bow, lovely lines.
     \end{trivlist}

math
====

Synopsis:

     \begin{math}
     MATH
     \end{math}

The math environment inserts given MATH material within the running text.  \(...\) and $...$ are synonyms. See Math formulas.

minipage
========

Synopses:

     \begin{minipage}{WIDTH}
       CONTENTS
     \end{minipage}

or

     \begin{minipage}[POSITION][HEIGHT][INNER-POS]{WIDTH}
       CONTENTS
     \end{minipage}

Put CONTENTS into a box that is WIDTH wide.  This is like a small version of a page; it can contain its own footnotes, itemized lists, etc. (There are some restrictions, including that it cannot have floats.)  This box will not be broken across pages.  So minipage is similar to \parbox (see \parbox) but here you can have paragraphs.

This example will be 3 inches wide, and has two paragraphs.

     \begin{minipage}{3in}
       Stephen Kleene was a founder of the Theory of Computation.

       He was a student of Church, wrote three influential texts,
       was President of the Association for Symbolic Logic,
       and won the National Medal of Science.
     \end{minipage}

See below for a discussion of the paragraph indent inside a minipage.

The required argument WIDTH is a rigid length (see Lengths). It gives the width of the box into which CONTENTS are typeset.

There are three optional arguments, POSITION, HEIGHT, and INNER-POS.  You need not include all three. For example, get the default POSITION and set the HEIGHT with \begin{minipage}[c][2.54cm] CONTENTS \end{minipage}. (Get the natural height with an empty argument, [].)

The optional argument POSITION governs how the minipage vertically aligns with the surrounding material.

c
     (synonym m) Default.  Positions the minipage so its vertical center lines up with the center of the adjacent text line (what Plain TeX calls \vcenter).

t
     Match the top line in the minipage with the baseline of the surrounding text (Plain TeX's \vtop.

b
     Match the bottom line in the minipage with the baseline of the surrounding text (Plain TeX's \vbox.

To see the effects of these, contrast running this

     ---\begin{minipage}[c]{0.25in}
       first\\ second\\ third
     \end{minipage}

with the results of changing c to b or t.

The optional argument HEIGHT is a rigid length (see Lengths). It sets the height of the minipage.  You can enter any value larger than, or equal to, or smaller than the minipage's natural height and LaTeX will not give an error or warning.  You can also set it to a height of zero or a negative value.

The final optional argument INNER-POS controls the placement of CONTENT inside the box. These are the possible values are (the default is the value of POSITION).

t
     Place CONTENT at the top of the box.

c
     Place it in the vertical center.

b
     Place it at the box bottom.

s
     Stretch CONTENTS out vertically; it must contain vertically stretchable space.

The INNER-POS argument makes sense when the HEIGHT option is set to a value larger than the minipage's natural height.  To see the effect of the options, run this example with the various choices in place of b.

     Text before
     \begin{center}
       ---\begin{minipage}[c][3in][b]{0.25\textwidth}
            first\\ second\\ third
       \end{minipage}
     \end{center}
     Text after

By default paragraphs are not indented in a minipage.  Change that with a command such as \setlength{\parindent}{1pc} at the start of CONTENTS.

Footnotes in a minipage environment are handled in a way that is particularly useful for putting footnotes in figures or tables.  A \footnote or \footnotetext command puts the footnote at the bottom of the minipage instead of at the bottom of the page, and it uses the \mpfootnote counter instead of the ordinary footnote counter (see Counters).

This puts the footnote at the bottom of the table, not the bottom of the page.

     \begin{center}           % center the minipage on the line
     \begin{minipage}{2.5in}
       \begin{center}         % center the table inside the minipage
         \begin{tabular}{ll}
           \textsc{Monarch}  &\textsc{Reign}             \\ \hline
           Elizabeth II      &63 years\footnote{to date} \\
           Victoria          &63 years                   \\
           George III        &59 years
         \end{tabular}
       \end{center}
     \end{minipage}
     \end{center}

If you nest minipages then there is an oddness when using footnotes. Footnotes appear at the bottom of the text ended by the next \end{minipage} which may not be their logical place.

This puts a table containing data side by side with a map graphic.  They are vertically centered.

     \newcommand*{\vcenteredhbox}[1]{\begin{tabular}{@{}c@{}}#1\end{tabular}}
       ...
     \begin{center}
       \vcenteredhbox{\includegraphics[width=0.3\textwidth]{nyc.png}}
       \hspace{0.1\textwidth}
       \begin{minipage}{0.5\textwidth}
         \begin{tabular}{r|l}
           \multicolumn{1}{r}{Borough} &Pop (million)  \\ \hline
           The Bronx      &$1.5$  \\
           Brooklyn       &$2.6$  \\
           Manhattan      &$1.6$  \\
           Queens         &$2.3$  \\
           Staten Island  &$0.5$
         \end{tabular}
       \end{minipage}
     \end{center}

picture
=======

Synopses:

     \begin{picture}(WIDTH,HEIGHT)
        PICTURE COMMANDS
     \end{picture}

or

     \begin{picture}(WIDTH,HEIGHT)(XOFFSET,YOFFSET)
       PICTURE COMMANDS
     \end{picture}

An environment to create simple pictures containing lines, arrows, boxes, circles, and text.  Note that while this environment is not obsolete, new documents typically use much more powerful graphics creation systems, such as TikZ, PSTricks, MetaPost, or Asymptote.  These are not covered in this document; see CTAN.

This shows the parallelogram law for adding vectors.

     \setlength{\unitlength}{1cm}
     \begin{picture}(6,6)      % picture box will be 6cm wide by 6cm tall
       \put(0,0){\vector(2,1){4}}  % for every 2 over this vector goes 1 up
         \put(2,1){\makebox(0,0)[l]{\ first leg}}
       \put(4,2){\vector(1,2){2}}
         \put(5,4){\makebox(0,0)[l]{\ second leg}}
       \put(0,0){\line(1,1){6}}
         \put(3,3){\makebox(0,0)[r]{sum\ }}
     \end{picture}

You can also use this environment to place arbitrary material at an exact location.

     \usepackage{color,graphicx}  % in preamble
       ...
     \begin{center}
     \setlength{\unitlength}{\textwidth}
     \begin{picture}(1,1)      % leave space, \textwidth wide and tall
       \put(0,0){\includegraphics[width=\textwidth]{desertedisland.jpg}}
       \put(0.25,0.35){\textcolor{red}{X Treasure here}}
     \end{picture}
     \end{center}

The red X will be precisely a quarter of the \linewidth from the left margin, and 0.35\linewidth up from the bottom.  Another example of this usage is to put similar code in the page header to get repeat material on each of a document's pages.

The picture environment has one required argument, a pair of numbers (WIDTH,HEIGHT).  Multiply these by the value \unitlength to get the nominal size of the output, the space that LaTeX reserves on the output page.  This nominal size need not be how large the picture really is; LaTeX will draw things from the picture outside the picture's box.

This environment also has an optional argument (XOFFSET,YOFFSET).  It is used to shift the origin.  Unlike most optional arguments, this one is not contained in square brackets. As with the required argument, it consists of two real numbers. Multiply these by \unitlength to get the point at the lower-left corner of the picture.

For example, if \unitlength has been set to 1mm, the command

     \begin{picture}(100,200)(10,20)

produces a box of width 100 millimeters and height 200 millimeters.  The picture's origin is the point (10mm,20mm) and so the lower-left corner is there, and the upper-right corner is at (110mm,220mm).  When you first draw a picture you typically omit the optional argument, leaving the origin at the lower-left corner.  If you then want to modify your picture by shifting everything, you can just add the appropriate optional argument.

Each PICTURE COMMAND tells LaTeX where to put something by naming its position.  A position is a pair such as (2.4,-5) giving the x- and y-coordinates.  A coordinate is a not a length, it is a real number (it may have a decimal point or a minus sign).  It specifies a length in multiples of the unit length \unitlength, so if \unitlength has been set to 1cm, then the coordinate 2.54 specifies a length of 2.54 centimeters.

LaTeX's default for \unitlength is 1pt.  it is a rigid length (see Lengths).  Change it with the \setlength command (see \setlength).  Make this change only outside of a picture environment.

Coordinates are given with respect to an origin, which is normally at the lower-left corner of the picture.  Note that when a position appears as an argument, as with \put(1,2){...}, it is not enclosed in braces since the parentheses serve to delimit the argument.  Also, unlike in some computer graphics systems, larger y-coordinates are further up the page.

There are four ways to put things in a picture: \put, \multiput, \qbezier, and \graphpaper.  The most often used is \put. This

     \put(11.3,-0.3){...}

places the object with its reference point at coordinates (11.3,-0.3).  The reference points for various objects will be described below. The \put command creates an LR box (see Modes). Anything that can go in an \mbox (see \mbox & \makebox) can go in the text argument of the \put command.  The reference point will be the lower left corner of the box.  In this picture

     \setlength{\unitlength}{1cm}
     ...\begin{picture}(1,1)
       \put(0,0){\line(1,0){1}}
       \put(0,0){\line(1,1){1}}
     \end{picture}

the three dots are just slightly left of the point of the angle formed by the two lines.  (Also, \line(1,1){1} does not call for a line of length one; rather the line has a change in the x coordinate of 1.)

The \multiput, qbezier, and graphpaper commands are described below.

This draws a rectangle with a wavy top, using \qbezier for that curve.

     \begin{picture}(3,1.5)
       \put(0,0){\vector(1,0){8}}  % x axis
       \put(0,0){\vector(0,1){4}}  % y axis
       \put(2,0){\line(0,1){3}}       % left side rectangle
       \put(4,0){\line(0,1){3.5}}     % right side
       \qbezier(2,3)(2.5,2.9)(3,3.25)
         \qbezier(3,3.25)(3.5,3.6)(4,3.5)
       \thicklines                 % below here, lines are twice as thick
       \put(2,3){\line(4,1){2}}
       \put(4.5,2.5){\framebox{Trapezoidal Rule}}
     \end{picture}

\put
----

Synopsis:

     \put(XCOORD,YCOORD){CONTENT}

Place CONTENT at the coordinate (XCOORD,YCOORD).  See the discussion of coordinates and \unitlength in picture. The CONTENT is processed in LR mode (see Modes) so it cannot contain line breaks.

This includes the text into the picture.

     \put(4.5,2.5){Apply the \textit{unpoke} move}

The reference point, the location (4.5,2.5), is the lower left of the text, at the bottom left of the A.

\multiput
---------

Synopsis:

     \multiput(X,Y)(DELTA_X,DELTA_Y){NUM-COPIES}{OBJ}

Copy OBJ a total of NUM-COPIES times, with an increment of DELTA_X,DELTA_Y.  The OBJ first appears at position (x,y), then at (x+\delta_x,y+\delta_y), and so on.

This draws a simple grid with every fifth line in bold (see also \graphpaper).

     \begin{picture}(10,10)
       \linethickness{0.05mm}
       \multiput(0,0)(1,0){10}{\line(0,1){10}}
       \multiput(0,0)(0,1){10}{\line(1,0){10}}
       \linethickness{0.5mm}
       \multiput(0,0)(5,0){3}{\line(0,1){10}}
       \multiput(0,0)(0,5){3}{\line(1,0){10}}
     \end{picture}

\qbezier
--------

Synopsis:

     \qbezier(X1,Y1)(X2,Y2)(X3,Y3)
     \qbezier[NUM](X1,Y1)(X2,Y2)(X3,Y3)

Draw a quadratic Bezier curve whose control points are given by the three required arguments (X1,Y1), (X2,Y2), and (X3,Y3).  That is, the curve runs from (X1,Y1) to (X3,Y3), is quadratic, and is such that the tangent line at (X1,Y1) passes through (X2,Y2), as does the tangent line at (X3,Y3).

This draws a curve from the coordinate (1,1) to (1,0).

     \qbezier(1,1)(1.25,0.75)(1,0)

The curve's tangent line at (1,1) contains (1.25,0.75), as does the curve's tangent line at (1,0).

The optional argument NUM gives the number of calculated intermediate points.  The default is to draw a smooth curve whose maximum number of points is \qbeziermax (change this value with \renewcommand).

\graphpaper
-----------

Synopsis:

     \graphpaper(X_INIT,Y_INIT)(X_DIMEN,Y_DIMEN)
     \graphpaper[SPACING](X_INIT,Y_INIT)(X_DIMEN,Y_DIMEN)

Draw a coordinate grid.  Requires the graphpap package. The grid's origin is (X_INIT,Y_INIT). Grid lines come every SPACING units (the default is 10). The grid extends X_DIMEN units to the right and Y_DIMEN units up. All arguments must be positive integers.

This make a grid with seven vertical lines and eleven horizontal lines.

     \usepackage{graphpap}    % in preamble
       ...
     \begin{picture}(6,20)    % in document body
       \graphpaper[2](0,0)(12,20)
     \end{picture}

The lines are numbered every ten units.

\line
-----

Synopsis:

     \line(X_RUN,Y_RISE){TRAVEL}

Draw a line.  It slopes such that it vertically rises Y_RISE for every horizontal X_RUN.  The TRAVEL is the total horizontal change --- it is not the length of the vector, it is the change in x.  In the special case of vertical lines, where (X_RUN,Y_RISE)=(0,1), the TRAVEL gives the change in y.

This draws a line starting at coordinates (1,3).

     \put(1,3){\line(2,5){4}}

For every over 2, this line will go up 5.  Because TRAVEL specifies that this goes over 4, it must go up 10.  Thus its endpoint is (1,3)+(4,10)=(5,13).  In particular, note that TRAVEL=4 is not the length of the line, it is the change in x.

The arguments X_RUN and Y_RISE are integers that can be positive, negative, or zero. (If both are 0 then LaTeX treats the second as 1.)  With \put(X_INIT,Y_INIT){\line(X_RUN,Y_RISE){TRAVEL}}, if X_RUN is negative then the line's ending point has a first coordinate that is less than X_INIT.  If Y_RISE is negative then the line's ending point has a second coordinate that is less than Y_INIT.

If TRAVEL is negative then you get LaTeX Error: Bad \line or \vector argument.

Standard LaTeX can only draw lines with a limited range of slopes because these lines are made by putting together line segments from pre-made fonts.  The two numbers X_RUN and Y_RISE must have integer values from -6 through 6.  Also, they must be relatively prime, so that (X_RUN,Y_RISE) can be (2,1) but not (4,2) (if you choose the latter then instead of lines you get sequences of arrowheads; the solution is to switch to the former).  To get lines of arbitrary slope and plenty of other shapes in a system like picture, see the package pict2e on CTAN.  Another solution is to use a full-featured graphics system such as TikZ, or PSTricks, or MetaPost, or Asymptote

\linethickness
--------------

Synopsis:

     \linethickness{DIM}

Declares the thickness of subsequent horizontal and vertical lines in a picture to be DIM, which must be a positive length (see Lengths).  It differs from \thinlines and \thicklines in that it does not affect the thickness of slanted lines, circles, or ovals.

\thinlines
----------

Declaration to set the thickness of subsequent lines, circles, and ovals in a picture environment to be 0.4pt.  This is the default thickness, so this command is unnecessary unless the thickness has been changed with either \linethickness or \thicklines.

\thicklines
-----------

Declaration to set the thickness of subsequent lines, circles, and ovals in a picture environment to be 0.8pt.  See also \linethickness and \thinlines.  This command is illustrated in the Trapezoidal Rule example of picture.

\circle
-------

Synopsis:

     \circle{DIAMETER}
     \circle*{DIAMETER}

Produces a circle with a diameter as close as possible to the specified one.  The * form produces a filled-in circle.

This draws a circle of radius 6, centered at (5,7).

     \put(5,7){\circle{6}}

The available radii for circle are, in points, the even numbers from 2 to 20, inclusive.  For circle* they are all the integers from 1 to 15.

\oval
-----

Synopsis:

     \oval(WIDTH,HEIGHT)
     \oval(WIDTH,HEIGHT)[PORTION]

Produce a rectangle with rounded corners.  The optional argument PORTION allows you to produce only half or a quarter of the oval. For half an oval take PORTION to be one of these.

t
     top half

b
     bottom half

r
     right half

l
     left half

Produce only one quarter of the oval by setting PORTION to tr, br, bl, or tl.

This draws the top half of an oval that is 3 wide and 7 tall.

     \put(5,7){\oval(3,7)[t]}

The (5,7) is the center of the entire oval, not just the center of the top half.

These shapes are not ellipses.  They are rectangles whose corners are made with quarter circles.  These circles have a maximum radius of 20pt (see \circle for the sizes).  Thus large ovals are just boxes with a small amount of corner rounding.

\shortstack
-----------

Synopsis:

     \shortstack[POSITION]{LINE 1 \\ ... }

Produce a vertical stack of objects.

This labels the y axis.

     \put(0,0){\vector(1,0){4}}   % x axis
     \put(0,0){\vector(0,1){2}}   % y
     \put(-0.25,2){\makebox[0][r]{\shortstack[r]{$y$\\ axis}}}

For a short stack, the reference point is the lower left of the stack. In the above example the \mbox & \makebox puts the stack flush right in a zero width box so in total the short stack sits slightly to the left of the y axis.

The valid positions are:

r
     Make objects flush right

l
     Make objects flush left

c
     Center objects (default)

Separate objects into lines with \\.  These stacks are short in that, unlike in a tabular or array environment, here the rows are not spaced out to be of even heights.  Thus, in \shortstack{X\\o\\o\\X} the first and last rows are taller than the middle two.  You can adjust row heights either by putting in the usual interline spacing with \shortstack{X\\ \strut o\\o\\X}, or by hand, via an explicit zero-width box \shortstack{X \\ \rule{0pt}{12pt} o\\o\\X} or by using \\'s optional argument \shortstack{X\\[2pt] o\\o\\X}.

The \shortstack command is also available outside the picture environment.

\vector
-------

Synopsis:

     \vector(X_RUN,Y_RISE){TRAVEL}

Draw a line ending in an arrow.  The slope of that line is: it vertically rises Y_RISE for every horizontal X_RUN.  The TRAVEL is the total horizontal change --- it is not the length of the vector, it is the change in x.  In the special case of vertical vectors, if (X_RUN,Y_RISE)=(0,1), then TRAVEL gives the change in y.

For an example see picture.

For elaboration on X_RUN and Y_RISE see \line.  As there, the values of X_RUN and Y_RISE are limited.  For \vector you must chooses integers between -4 and 4, inclusive.  Also, the two you choose must be relatively prime.  Thus, \vector(2,1){4} is acceptable but \vector(4,2){4} is not (if you use the latter then you get a sequence of arrowheads).

\makebox (picture)
------------------

Synopsis:

     \makebox(REC-WIDTH,REC-HEIGHT){TEXT}
     \makebox(REC-WIDTH,REC-HEIGHT)[POSITION]{TEXT}

Make a box to hold TEXT.  This command fits with the picture environment, although you can use it outside of there, because REC-WIDTH and REC-HEIGHT are numbers specifying distances in terms of the \unitlength (see picture).  This command is similar to the normal \makebox command (see \mbox & \makebox) except here that you must specify the width and height.  This command is fragile (see \protect).

This makes a box of length 3.5 times \unitlength and height 4 times \unitlength.

     \put(1,2){\makebox(3.5,4){...}}

The optional argument POSITION specifies where in the box the TEXT appears.  The default is to center it, both horizontally and vertically.  To place it somewhere else, use a string with one or two of these letters.

t
     Puts TEXT the top of the box.

b
     Put TEXT at the bottom.

l
     Put TEXT on the left.

r
     Put TEXT on the right.

\framebox (picture)
-------------------

Synopsis:

     \framebox(REC-WIDTH,REC-HEIGHT){TEXT}
     \framebox(REC-WIDTH,REC-HEIGHT)[POSITION]{TEXT}

This is the same as \makebox (picture) except that it puts a frame around the outside of the box that it creates.  The reference point is the bottom left corner of the frame.  This command fits with the picture environment, although you can use it outside of there, because lengths are numbers specifying the distance in terms of the \unitlength (see picture).  This command is fragile (see \protect).

This example creates a frame 2.5 inches by 3 inches and puts the text in the center.

     \setlength{\unitlength}{1in}
     \framebox(2.5,3){test text}

The required arguments are that the rectangle has overall width RECT-WIDTH units and height RECT-HEIGHT units.

The optional argument POSITION specifies the position of TEXT; see \makebox (picture) for the values that it can take.

The rule has thickness \fboxrule and there is a blank space \fboxsep between the frame and the contents of the box.

For this command, you must specify the WIDTH and HEIGHT.  If you want to just put a frame around some contents whose dimension is determined in some other way then either use \fbox (see \fbox & \framebox) or \frame (see \frame).

\frame
------

Synopsis:

     \frame{CONTENTS}

Puts a rectangular frame around CONTENTS.  The reference point is the bottom left corner of the frame.  In contrast to \framebox (see \framebox (picture)), this command puts no extra space is put between the frame and the object.  It is fragile (see \protect).

\dashbox
--------

Synopsis:

     \dashbox{DASH-LEN}(RECT-WIDTH,RECT-HEIGHT){TEXT}
     \dashbox{DASH-LEN}(RECT-WIDTH,RECT-HEIGHT)[POSITION]{TEXT}

Create a dashed rectangle around TEXT.  This command fits with the picture environment, although you can use it outside of there, because lengths are numbers specifying the distance in terms of the \unitlength (see picture).

The required arguments are: dashes are DASH-LEN units long, with the same length gap, and the rectangle has overall width RECT-WIDTH units and height RECT-HEIGHT units.

The optional argument POSITION specifies the position of TEXT; see \makebox (picture) for the values that it can take.

This shows that you can use non-integer value for DASH-LEN.

     \put(0,0){\dashbox{0.1}(5,0.5){My hovercraft is full of eels.}}

Each dash will be 0.1\unitlength long, the box's width is 5\unitlength and its height is 0.5\unitlength.

As in that example, a dashed box looks best when RECT-WIDTH and RECT-HEIGHT are multiples of the DASH-LEN.

quotation & quote
=================

Synopsis:

     \begin{quotation}
       TEXT
     \end{quotation}

or

     \begin{quote}
       TEXT
     \end{quote}

Include a quotation. Both environments indent margins on both sides by \leftmargin and the text is right-justified.

They differ in how they treat paragraphs. In the quotation environment, paragraphs are indented by 1.5em and the space between paragraphs is small, 0pt plus 1pt.  In the quote environment, paragraphs are not indented and there is vertical space between paragraphs (it is the rubber length \parsep).

     \begin{quotation} \small\it
       Four score and seven years ago
       ... shall not perish from the earth.
       \hspace{1em plus 1fill}---Abraham Lincoln
     \end{quotation}

tabbing
=======

Synopsis:

     \begin{tabbing}
     ROW1COL1 \= ROW1COL2 ...  \\
     ROW2COL1 \> ROW2COL2 ...  \\
     ...
     \end{tabbing}

Align text in columns, by setting tab stops and tabbing to them much as was done on a typewriter.  This is less often used than the environments tabular (see tabular) or array (see array) because in those the width of each column need not be constant and need not be known in advance.

This example has a first line where the tab stops are set to explicit widths, ended by a \kill command (which is described below):

     \begin{tabbing}
     \hspace{0.75in}     \= \hspace{0.40in}  \= \hspace{0.40in}    \kill
     Ship                \> Guns             \> Year    \\
     \textit{Sophie}     \> 14               \> 1800    \\
     \textit{Polychrest} \> 24               \> 1803    \\
     \textit{Lively}     \> 38               \> 1804    \\
     \textit{Surprise}   \> 28               \> 1805    \\
     \end{tabbing}

Both the tabbing environment and the more widely-used tabular environment put text in columns.  The most important distinction is that in tabular the width of columns is determined automatically by LaTeX, while in tabbing the user sets the tab stops.  Another distinction is that tabular generates a box, but tabbing can be broken across pages. Finally, while tabular can be used in any mode, tabbing can be used only in paragraph mode and it starts a new paragraph.

A tabbing environment always starts a new paragraph, without indentation. Moreover, as shown in the example above, there is no need to use the starred form of the \hspace command at the beginning of a tabbed row.  The right margin of the tabbing environment is the end of line, so that the width of the environment is \linewidth.

The tabbing environment contains a sequence of tabbed rows.  The first tabbed row begins immediately after \begin{tabbing} and each row ends with \\ or \kill. The last row may omit the \\ and end with just \end{tabbing}.

At any point the tabbing environment has a current tab stop pattern, a sequence of N > 0 tab stops, numbered 0, 1, etc.  These create N corresponding columns.  Tab stop 0 is always the left margin, defined by the enclosing environment.  Tab stop number I is set if it is assigned a horizontal position on the page.  Tab stop number I can only be set if all the stops 0, ..., i-1 have already been set; normally later stops are to the right of earlier ones.

By default any text typeset in a tabbing environment is typeset ragged right and left-aligned on the current tab stop. Typesetting is done in LR mode (see Modes).

The following commands can be used inside a tabbing environment. They are all fragile (see \protect).

\\ (tabbing)
     End a tabbed line and typeset it.

\= (tabbing)
     Sets a tab stop at the current position.

\> (tabbing)
     Advances to the next tab stop.

\<
     Put following text to the left of the local margin (without changing the margin).  Can only be used at the start of the line.

\+
     Moves the left margin of the next and all the following commands one tab stop to the right, beginning tabbed line if necessary.

\-
     Moves the left margin of the next and all the following commands one tab stop to the left, beginning tabbed line if necessary.

\' (tabbing)
     Moves everything that you have typed so far in the current column, i.e., everything from the most recent \>, \<, \', \\, or \kill command, to the previous column and aligned to the right, flush against the current column's tab stop.

\` (tabbing)
     Allows you to put text flush right against any tab stop, including tab stop 0.  However, it can't move text to the right of the last column because there's no tab stop there.  The \` command moves all the text that follows it, up to the \\ or \end{tabbing} command that ends the line, to the right margin of the tabbing environment.  There must be no \> or \' command between the \` and the \\ or \end{tabbing} command that ends the line.

\a (tabbing)
     In a tabbing environment, the commands \=, \' and \` do not produce accents as usual (see Accents).  Instead, use the commands \a=, \a' and \a`.

\kill
     Sets tab stops without producing text.  Works just like \\ except that it throws away the current line instead of producing output for it. Any \=, \+ or \- commands in that line remain in effect.

\poptabs
     Restores the tab stop positions saved by the last \pushtabs.

\pushtabs
     Saves all current tab stop positions. Useful for temporarily changing tab stop positions in the middle of a tabbing environment.

\tabbingsep
     Distance of the text moved by \' to left of current tab stop.

This example typesets a Pascal function:

     \begin{tabbing}
     function \= fact(n : integer) : integer;\\
              \> begin \= \+ \\
                    \> if \= n > 1 then \+ \\
                             fact := n * fact(n-1) \- \\
                       else \+ \\
                             fact := 1; \-\- \\
                 end;\\
     \end{tabbing}

The output looks like this.

     function fact(n : integer) : integer;
              begin
                    if n > 1 then
                       fact := n * fact(n-1);
                    else
                       fact := 1;
              end;

algorithm2e listings minted

This example is just for illustration of the environment.  To actually typeset computer code in typewriter like this, a verbatim environment (see verbatim) would normally be best.  For pretty-printed code, there are quite a few packages, including algorithm2e, fancyvrb, listings, and minted.

table
=====

Synopsis:

     \begin{table}[PLACEMENT]
       TABLE BODY
       \caption[LOFTITLE]{TITLE}  % optional
       \label{LABEL}              % also optional
     \end{table}

A class of floats (see Floats).  They cannot be split across pages and so they are not typeset in sequence with the normal text but instead are floated to a convenient place, such as the top of a following page.

This example table environment contains a tabular

     \begin{table}
       \centering\small
       \begin{tabular}{ll}
         \multicolumn{1}{c}{\textit{Author}}
           &\multicolumn{1}{c}{\textit{Piece}}  \\ \hline
         Bach            &Cello Suite Number 1  \\
         Beethoven       &Cello Sonata Number 3 \\
         Brahms          &Cello Sonata Number 1
       \end{tabular}
       \caption{Top cello pieces}
       \label{tab:cello}
     \end{table}

but you can put many different kinds of content in a table, including text, LaTeX commands, etc.

For the possible values of PLACEMENT and their effect on the float placement algorithm, see Floats.

The table body is typeset in a parbox of width \textwidth. It can contain text, commands, graphics, etc.

The label is optional; it is used for cross references (see Cross references). The \caption command is also optional.  It specifies caption text for the table.  By default it is numbered.  If its optional LOTTITLE is present then that text is used in the list of tables instead of TITLE (see Table of contents etc.).

In this example the table and caption will float to the bottom of a page, unless it is pushed to a float page at the end.

     \begin{table}[b]
       \centering
       \begin{tabular}{r|p{2in}} \hline
         One &The loneliest number \\
         Two &Can be as sad as one.
              It's the loneliest number since the number one.
       \end{tabular}
       \caption{Cardinal virtues}
       \label{tab:CardinalVirtues}
     \end{table}

tabular
=======

Synopsis:

     \begin{tabular}[POS]{COLS}
       COLUMN 1 ENTRY  &COLUMN 2 ENTRY  ...  &COLUMN N ENTRY \\
       ...
     \end{tabular}

or

     \begin{tabular*}{WIDTH}[POS]{COLS}
       COLUMN 1 ENTRY  &COLUMN 2 ENTRY  ...  &COLUMN N ENTRY \\
       ...
     \end{tabular*}

Produce a table, a box consisting of a sequence of horizontal rows. Each row consists of items that are aligned vertically in columns.  This illustrates many of the features.

     \begin{tabular}{l|l}
       \textit{Player name}  &\textit{Career home runs}  \\
       \hline
       Hank Aaron  &755 \\
       Babe Ruth   &714
     \end{tabular}

The output will have two left-aligned columns with a vertical bar between them.  This is specified in tabular's argument {l|l}. Put the entries into different columns by separating them with an ampersand, &.  The end of each row is marked with a double backslash, \\.  Put a horizontal rule below a row, after a double backslash, with \hline. After the last row the \\ is optional, unless an \hline command follows to put a rule below the table.

The required and optional arguments to tabular consist of:

pos
     Optional.  Specifies the table's vertical position.  The default is to align the table so its vertical center matches the baseline of the surrounding text.  There are two other possible alignments: t aligns the table so its top row matches the baseline of the surrounding text, and b aligns on the bottom row.

     This only has an effect if there is other text.  In the common case of a tabular alone in a center environment this option makes no difference.

cols
     Required.  Specifies the formatting of columns.  It consists of a sequence of the following specifiers, corresponding to the types of column and intercolumn material.

     l
          A column of left-aligned items.

     r
          A column of right-aligned items.

     c
          A column of centered items.

     |
          A vertical line the full height and depth of the environment.

     @{TEXT OR SPACE}
          Insert TEXT OR SPACE at this location in every row.  The TEXT OR SPACE material is typeset in LR mode.  This text is fragile (see \protect).

          If between two columns there is no @-expression then LaTeX's book, article, and report classes will put on either side of each column a space of length \tabcolsep, which by default is 6pt.  That is, by default adjacent columns are separated by 12pt (so \tabcolsep is misleadingly named since it is only half of the separation between tabular columns).  In addition, a space of 6pt also comes before the first column and after the final column, unless you put a @{...} or | there.

          If you override the default and use an @-expression then LaTeX does not insert \tabcolsep so you must insert any desired space yourself, as in @{\hspace{1em}}.

          An empty expression @{} will eliminate the space. In particular, sometimes you want to eliminate the space before the first column or after the last one, as in the example below where the tabular lines need to lie on the left margin.

               \begin{flushleft}
                 \begin{tabular}{@{}l}
                   ...
                 \end{tabular}
               \end{flushleft}

          The next example shows text, a decimal point between the columns, arranged so the numbers in the table are aligned on it.

               \begin{tabular}{r@{$.$}l}
                 $3$ &$14$  \\
                 $9$ &$80665$
               \end{tabular}

          An \extracolsep{WD} command in an @-expression causes an extra space of width WD to appear to the left of all subsequent columns, until countermanded by another \extracolsep.  Unlike ordinary intercolumn space, this extra space is not suppressed by an @-expression.  An \extracolsep command can be used only in an @-expression in the cols argument.  Below, LaTeX inserts the right amount of intercolumn space to make the entire table 4 inches wide.

               \begin{tabular*}{4in}{l@{\extracolsep{\fill}}l}
                 Seven times down, eight times up \ldots
                 &such is life!
               \end{tabular*}

          To insert commands that are automatically executed before a given column, load the array package and use the >{...} specifier.

     p{WD}
          Each item in the column is typeset in a parbox of width WD, as if it were the argument of a \parbox[t]{wd}{...} command.

          A line break double backslash \\ may not appear in the item, except inside an environment like minipage, array, or tabular, or inside an explicit \parbox, or in the scope of a \centering, \raggedright, or \raggedleft declaration (when used in a p-column element these declarations must appear inside braces, as with {\centering .. \\ ..}). Otherwise LaTeX will misinterpret the double backslash as ending the row.  Instead, to get a line break in there use \newline (see \newline).

     *{NUM}{COLS}
          Equivalent to NUM copies of COLS, where NUM is a positive integer and COLS is a list of specifiers.  Thus the specifier \begin{tabular}{|*{3}{l|r}|} is equivalent to the specifier \begin{tabular}{|l|rl|rl|r|}.  Note that COLS may contain another *-expression.

width
     Required for tabular*, not allowed for tabular. Specifies the width of the tabular* environment.  The space between columns should be rubber, as with @{\extracolsep{\fill}}, to allow the table to stretch or shrink to make the specified width, or else you are likely to get the Underfull \hbox (badness 10000) in alignment ... warning.

Parameters that control formatting:

\arrayrulewidth
     A length that is the thickness of the rule created by |, \hline, and \vline in the tabular and array environments.  The default is .4pt. Change it as in \setlength{\arrayrulewidth}{0.8pt}.

\arraystretch
     A factor by which the spacing between rows in the tabular and array environments is multiplied.  The default is 1, for no scaling.  Change it as \renewcommand{\arraystretch}{1.2}.

\doublerulesep
     A length that is the distance between the vertical rules produced by the || specifier.  The default is 2pt.

\tabcolsep
     A length that is half of the space between columns. The default is 6pt.  Change it with \setlength.

The following commands can be used inside the body of a tabular environment, the first two inside an entry and the second two between lines:

\multicolumn
------------

Synopsis:

     \multicolumn{NUMCOLS}{COLS}{TEXT}

Make an array or tabular entry that spans several columns. The first argument NUMCOLS gives the number of columns to span. The second argument COLS specifies the formatting of the entry, with c for centered, l for flush left, or r for flush right.  The third argument TEXT gives the contents of that entry.

In this example, in the first row, the second and third columns are spanned by the single heading Name.

     \begin{tabular}{lccl}
       \textit{ID}       &\multicolumn{2}{c}{\textit{Name}} &\textit{Age} \\
       \hline
       978-0-393-03701-2 &O'Brian &Patrick                  &55           \\
         ...
     \end{tabular}

What counts as a column is: the column format specifier for the array or tabular environment is broken into parts, where each part (except the first) begins with l, c, r, or p.  So from \begin{tabular}{|r|ccp{1.5in}|} the parts are |r|, c, c, and p{1.5in}|.

The COLS argument overrides the array or tabular environment's intercolumn area default adjoining this multicolumn entry. To affect that area, this argument can contain vertical bars | indicating the placement of vertical rules, and @{...} expressions.  Thus if COLS is |c| then this multicolumn entry will be centered and a vertical rule will come in the intercolumn area before it and after it.  This table details the exact behavior.

     \begin{tabular}{|cc|c|c|}
       \multicolumn{1}{r}{w}       % entry one
         &\multicolumn{1}{|r|}{x}  % entry two
         &\multicolumn{1}{|r}{y}   % entry three
         &z                        % entry four
     \end{tabular}

Before the first entry the output will not have a vertical rule because the \multicolumn has the COLS specifier r with no initial vertical bar.  Between entry one and entry two there will be a vertical rule; although the first COLS does not have an ending vertical bar, the second COLS does have a starting one.  Between entry two and entry three there is a single vertical rule; despite that the COLS in both of the surrounding multicolumn's call for a vertical rule, you only get one rule.  Between entry three and entry four there is no vertical rule; the default calls for one but the COLS in the entry three \multicolumn leaves it out, and that takes precedence.  Finally, following entry four there is a vertical rule because of the default.

The number of spanned columns NUMCOLS can be 1.  Besides giving the ability to change the horizontal alignment, this also is useful to override for one row the tabular definition's default intercolumn area specification, including the placement of vertical rules.

In the example below, in the tabular definition the first column is specified to default to left justified but in the first row the entry is centered with \multicolumn{1}{c}{\textsc{Period}}. Also in the first row, the second and third columns are spanned by a single entry with \multicolumn{2}{c}{\textsc{Span}}, overriding the specification to center those two columns on the page range en-dash.

     \begin{tabular}{l|r@{--}l}
       \multicolumn{1}{c}{\textsc{Period}}
         &multicolumn{2}{c}{\textsc{Span}} \\ \hline
       Baroque          &1600           &1760         \\
       Classical        &1730           &1820         \\
       Romantic         &1780           &1910         \\
       Impressionistic  &1875           &1925
     \end{tabular}

Although the tabular specification by default puts a vertical rule between the first and second columns, no such vertical rule appears in the first row here.  That's because there is no vertical bar in the COLS part of the first row's first \multicolumn command.

\vline
------

Draw a vertical line in a tabular or array environment extending the full height and depth of an entry's row.  Can also be used in an @-expression, although its synonym vertical bar | is more common.  This command is rarely used in the body of a table; typically a table's vertical lines are specified in tabular's COLS argument and overridden as needed with \multicolumn (see tabular).

The example below illustrates some pitfalls.  In the first row's second entry the \hfill moves the \vline to the left edge of the cell.  But that is different than putting it halfway between the two columns, so between the first and second columns there are two vertical rules, with the one from the {c|cc} specifier coming before the one produced by the \vline\hfill.  In contrast, the first row's third entry shows the usual way to put a vertical bar between two columns.  In the second row, the ghi is the widest entry in its column so in the \vline\hfill the \hfill has no effect and the vertical line in that entry appears immediately next to the g, with no whitespace.

     \begin{tabular}{c|cc}
       x   &\vline\hfill y   &\multicolumn{1}{|r}{z} \\ % row 1
       abc &def &\vline\hfill ghi                       % row 2
     \end{tabular}

\cline
------

Synopsis:

     \cline{I-J}

In an array or tabular environment, draw a horizontal rule beginning in column I and ending in column J. The dash, -, must appear in the mandatory argument. To span a single column use the number twice, as with \cline{2-2}.

This example puts two horizontal lines between the first and second rows, one line in the first column only, and the other spanning the third and fourth columns.  The two lines are side-by-side, at the same height.

     \begin{tabular}{llrr}
       a &b &c &d \\ \cline{1-1} \cline{3-4}
       e &f &g &h
     \end{tabular}

\hline
------

Draw a horizontal line the width of the enclosing tabular or array environment.  It's most commonly used to draw a line at the top, bottom, and between the rows of a table.

In this example the top of the table has two horizontal rules, one above the other, that span both columns.  The bottom of the table has a single rule spanning both columns.  Because of the \hline, the tabular second row's line ending double backslash \\ is required.

     \begin{tabular}{ll} \hline\hline
       Baseball   &Red Sox  \\
       Basketball &Celtics  \\ \hline
     \end{tabular}

thebibliography
===============

Synopsis:

     \begin{thebibliography}{WIDEST-LABEL}
       \bibitem[LABEL]{CITE_KEY}
       ...
     \end{thebibliography}

Produce a bibliography or reference list.  There are two ways to produce bibliographic lists.  This environment is suitable when you have only a few references and can maintain the list by hand.  See Using BibTeX for a more sophisticated approach.

This shows the environment with two entries.

     This work is based on \cite{latexdps}.
     Together they are \cite{latexdps, texbook}.
       ...
     \begin{thebibliography}{9}
     \bibitem{latexdps}
       Leslie Lamport.
       \textit{\LaTeX{}: a document preparation system}.
       Addison-Wesley, Reading, Massachusetts, 1993.
     \bibitem{texbook}
       Donald Ervin Knuth.
       \textit{The \TeX book}.
       Addison-Wesley, Reading, Massachusetts, 1983.
     \end{thebibliography}

This styles the first reference as [1] Leslie ..., and so that \cite{latexdps} produces the matching ... based on [1]. The second \cite produces [1, 2].  You must compile the document twice to resolve these references.

The mandatory argument WIDEST-LABEL is text that, when typeset, is as wide as the widest item label produced by the \bibitem commands.  The tradition is to use 9 for bibliographies with less than 10 references, 99 for ones with less than 100, etc.

The bibliographic list is headed by a title such as Bibliography. To change it there are two cases.  In the book and report classes, where the top level sectioning is \chapter and the default title is Bibliography, that title is in the macro \bibname.  For article, where the class's top level sectioning is \section and the default is References, the title is in macro \refname.  Change it by redefining the command, as with \renewcommand{\refname}{Cited references} after \begin{document}.

Language support packages such as babel will automatically redefine \refname or \bibname to fit the selected language.

\bibitem
--------

Synopsis:

     \bibitem{CITE_KEY}

or

     \bibitem[LABEL]{CITE_KEY}

Generate an entry labeled by LABEL.  The default is for LaTeX to generates a number using the enumi counter.  The citation key CITE_KEY is a string of letters, numbers, and punctuation symbols (but not comma).

See thebibliography for an example.

The optional LABEL changes the default label from an integer to the given string.  With this

     \begin{thebibliography}
     \bibitem[Lamport 1993]{latexdps}
       Leslie Lamport.
       \textit{\LaTeX{}: a document preparation system}.
       Addison-Wesley, Reading, Massachusetts, 1993.
     \bibitem{texbook}
       Donald Ervin Knuth.
       \textit{The \TeX book}.
       Addison-Wesley, Reading, Massachusetts, 1983.
     \end{thebibliography}

the first entry will be styled as [Lamport 1993] Leslie ...  (The amount of horizontal space that LaTeX leaves for the label depends on the WIDEST-LABEL argument of the thebibliography environment; see thebibliography.)  Similarly, ... based on \cite{latexdps} will produce ... based on [Lamport 1994].

If you mix \bibitem entries having a LABEL with those that do not then LaTeX will number the unlabelled ones sequentially.  In the example above the texbook entry will appear as [1] Donald ..., despite that it is the second entry.

If you use the same CITE_KEY twice then you get LaTeX Warning: There were multiply-defined labels.

Under the hood, LaTeX remembers the CITE_KEY and LABEL information because \bibitem writes it to the auxiliary file FILENAME.aux.  For instance, the above example causes \bibcite{latexdps}{Lamport, 1993} and \bibcite{texbook}{1} to appear in that file.  The .aux file is read by the \begin{document} command and then the information is available for \cite commands.  This explains why you need to run LaTeX twice to resolve references: once to write it out and once to read it in.

Because of this two-pass algorithm, when you add a \bibitem or change its CITE_KEY you may get LaTeX Warning: Label(s) may have changed. Rerun to get cross-references right.  Fix it by recompiling.

\cite
-----

Synopsis:

     \cite{KEYS}

or

     \cite[SUBCITE]{KEYS}

Generate as output a citation to the references associated with KEYS.  The mandatory KEYS is a citation key, or a comma-separated list of citation keys (see \bibitem).

This

     The ultimate source is \cite{texbook}.
       ...
     \begin{thebibliography}
     \bibitem{texbook}
       Donald Ervin Knuth.
       \textit{The \TeX book}.
       Addison-Wesley, Reading, Massachusetts, 1983.
     \end{thebibliography}

produces output like ... source is [1].  (You can change the appearance of the citation with bibliography styles.  More is in Using BibTeX.)

The optional argument SUBCITE is appended to the citation.  For example, See 14.3 in \cite[p.~314]{texbook} might produce See 14.3 in [1, p. 314].

In addition to what appears in the output, \cite writes information to the auxiliary file FILENAME.aux.  For instance, \cite{latexdps} writes \citation{latexdps} to that file.  This information is used by BibTeX to include in your reference list only those works that you have actually cited; see \nocite also.

If KEYS is not in your bibliography information then you get LaTeX Warning: There were undefined references, and in the output the citation shows as a boldface question mark between square brackets. There are two possible causes.  If you have mistyped something, as in \cite{texbok} then you need to correct the spelling.  On the other hand, if you have just added or modified the bibliographic information and so changed the .aux file (see \bibitem) then the fix may be to run LaTeX again.

\nocite
-------

Synopsis:

     \nocite{KEYS}

Produces no output but writes KEYS to the auxiliary file DOC-FILENAME.aux.

The mandatory argument KEYS is a comma-separated list of one or more citation keys (see \bibitem).  This information is used by BibTeX to include these works in your reference list even though you have not cited them (see \cite).

Using BibTeX
------------

As described in thebibliography (see thebibliography), a sophisticated approach to managing bibliographies is provided by the BibTeX program.  This is only an introduction; see the full documentation on CTAN.

With BibTeX, you don't use thebibliography (see thebibliography). Instead, include these lines.

     \bibliographystyle{BIBSTYLE}
     \bibliography{BIBFILE1, BIBFILE2, ...}

The BIBSTYLE refers to a file BIBSTYLE.bst, which defines how your citations will look.  The standard BIBSTYLE's distributed with BibTeX are:

alpha
     Labels are formed from name of author and year of publication. The bibliographic items are sorted alphabetically.

plain
     Labels are integers. Sort the  bibliographic items alphabetically.

unsrt
     Like plain, but entries are in order of citation.

abbrv
     Like plain, but more compact labels.

Many, many other BibTeX style files exist, tailored to the demands of various publications.  See CTAN's listing http://mirror.ctan.org/biblio/bibtex/contrib.

The \bibliography command is what actually produces the bibliography.  Its argument is a comma-separated list, referring to files named BIBFILE1.bib, BIBFILE2.bib, ... These contain your database in BibTeX format.  This shows a typical couple of entries in that format.

     @book{texbook,
       title     = {The {{\TeX}}book},
       author    = {D.E. Knuth},
       isbn      = {0201134489},
       series    = {Computers \& typesetting},
       year      = {1983},
       publisher = {Addison-Wesley}
     }
     @book{sexbook,
         author    = {W.H. Masters and V.E. Johnson},
         title     = {Human Sexual Response},
         year      = {1966},
         publisher = {Bantam Books}
     }

Only the bibliographic entries referred to via \cite and \nocite will be listed in the document's bibliography.  Thus you can keep all your sources together in one file, or a small number of files, and rely on BibTeX to include in this document only those that you used.

theorem
=======

Synopsis:

     \begin{theorem}
       THEOREM BODY
     \end{theorem}

Produces Theorem N in boldface followed by THEOREM BODY in italics.  The numbering possibilities for N are described under \newtheorem (see \newtheorem).

     \newtheorem{lem}{Lemma}      % in preamble
     \newtheorem{thm}{Theorem}
       ...
     \begin{lem}                  % in  document body
       text of lemma
     \end{lem}

     The next result follows immediately.
     \begin{thm}[Gauss]   %  put `Gauss' in parens after theorem head
       text of theorem
     \end{thm}

Most new documents use the packages amsthm and amsmath from the American Mathematical Society.  Among other things these packages include a large number of options for theorem environments, such as styling options.

titlepage
=========

Synopsis:

     \begin{titlepage}
       ... text and spacing ...
     \end{titlepage}

Create a title page, a page with no printed page number or heading and with succeeding pages numbered starting with page one.

In this example all formatting, including vertical spacing, is left to the author.

     \begin{titlepage}
     \vspace*{\stretch{1}}
     \begin{center}
       {\huge\bfseries Thesis \\[1ex]
                       title}                  \\[6.5ex]
       {\large\bfseries Author name}           \\
       \vspace{4ex}
       Thesis  submitted to                    \\[5pt]
       \textit{University name}                \\[2cm]
       in partial fulfilment for the award of the degree of \\[2cm]
       \textsc{\Large Doctor of Philosophy}    \\[2ex]
       \textsc{\large Mathematics}             \\[12ex]
       \vfill
       Department of Mathematics               \\
       Address                                 \\
       \vfill
       \today
     \end{center}
     \vspace{\stretch{2}}
     \end{titlepage}

To instead produce a standard title page without a titlepage environment, use \maketitle (see \maketitle).

verbatim
========

Synopsis:

     \begin{verbatim}
     LITERAL-TEXT
     \end{verbatim}

A paragraph-making environment in which LaTeX produces as output exactly what you type as input.  For instance inside LITERAL-TEXT the backslash \ character does not start commands, it produces a printed \, and carriage returns and blanks are taken literally.  The output appears in a monospaced typewriter-like font (\tt).

     \begin{verbatim}
     Symbol swearing: %&$#?!.
     \end{verbatim}

The only restriction on literal-text is that it cannot include the string \end{verbatim}.

You cannot use the verbatim environment in the argument to macros, for instance in the argument to a \section.  This is not the same as commands being fragile (see \protect), instead it just cannot appear there. (But the cprotect package can help with this.)

One common use of verbatim input is to typeset computer code.  There are packages that are an improvement the verbatim environment.  For instance, one improvement is to allow the verbatim inclusion of external files, or parts of those files.  Such packages include listings, and minted.

A package that provides many more options for verbatim environments is fancyvrb.  Another is verbatimbox.

For a list of all the relevant packages, see CTAN.

\verb
-----

Synopsis:

     \verb CHAR LITERAL-TEXT CHAR
     \verb* CHAR LITERAL-TEXT CHAR

Typeset LITERAL-TEXT as it is input, including special characters and spaces, using the typewriter (\tt) font.

This example shows two different invocations of \verb.

     This is \verb!literally! the biggest pumpkin ever.
     And this is the best squash, \verb+literally!+

The first \verb has its LITERAL-TEXT surrounded with exclamation point, !.  The second instead uses plus, +, because the exclamation point is part of literal-text.

The single-character delimiter CHAR surrounds LITERAL-TEXT --- it must be the same character before and after.  No spaces come between \verb or \verb* and CHAR, or between CHAR and LITERAL-TEXT, or between LITERAL-TEXT and the second occurrence of CHAR (the synopsis shows a space only to distinguish one component from the other).  The delimiter must not appear in LITERAL-TEXT. The LITERAL-TEXT cannot include a line break.

The *-form differs only in that spaces are printed with a visible space character.

The output from this will include a character showing the spaces.

     The commands's first argument is \verb*!filename with extension! and ...

For typesetting Internet addresses, urls, the package url provides an option that is better than the \verb command, since it allows line breaks.

For computer code there are many packages with advantages over \verb.  One is listings, another is minted.

You cannot use \verb in the argument to a macro, for instance in the argument to a \section.  It is not a question of \verb being fragile (see \protect), instead it just cannot appear there. (But the cprotect package can help with this.)

verse
=====

Synopsis:

     \begin{verse}
       LINE1 \\
       LINE2 \\
       ...
     \end{verse}

An environment for poetry.

Here are two lines from Shakespeare's Romeo and Juliet.

     Then plainly know my heart's dear love is set \\
     On the fair daughter of rich Capulet.

Separate the lines of each stanza with \\, and use one or more blank lines to separate the stanzas.

     \begin{verse}
     \makebox[\linewidth][c]{\textit{Shut Not Your Doors} ---Walt Whitman}
       \\[1\baselineskip]
     Shut not your doors to me proud libraries,                  \\
     For that which was lacking on all your well-fill'd shelves, \\
     \qquad yet needed most, I bring,                             \\
     Forth from the war emerging, a book I have made,            \\
     The words of my book nothing, the drift of it every thing,  \\
     A book separate, not link'd with the rest nor felt by the intellect, \\
     But you ye untold latencies will thrill to every page.
     \end{verse}

The output has margins indented on the left and the right, paragraphs are not indented, and the text is not right-justified.

Line breaking
*************

The first thing LaTeX does when processing ordinary text is to translate your input file into a sequence of glyphs and spaces.  To produce a printed document, this sequence must be broken into lines (and these lines must be broken into pages).

LaTeX usually does the line (and page) breaking in the text body for you but in some environments you manually force line breaks.

A common workflow is to get a final version of the document content before taking a final pass through and considering line breaks (and page breaks).  This differs from word processing, where you are formatting text as you input it.  Putting these off until the end prevents a lot of fiddling with breaks that will change anyway.

\\
==

Synopsis, one of:

     \\
     \\[MORESPACE]

or one of:

     \\*
     \\*[MORESPACE]

End the current line.  The optional argument MORESPACE specifies extra vertical space to be inserted before the next line.  This is a rubber length (see Lengths) and can be negative.  The text before the line break is set at its normal length, that is, it is not stretched to fill out the line width.  This command is fragile (see \protect).

The starred form, \\*, tells LaTeX not to start a new page between the two lines, by issuing a \nobreak.

     \title{My story: \\[0.25in]
            a tale of woe}

Explicit line breaks in the main text body are unusual in LaTeX.  In particular, don't start new paragraphs with \\.  Instead leave a blank line between the two paragraphs.  And don't put in a sequence of \\'s to make vertical space. Instead use \vspace{LENGTH}, or \leavevmode\vspace{LENGTH}, or \vspace*{LENGTH} if you want the space to not be thrown out at the top of a new page (see \vspace).

The \\ command is mostly used outside of the main flow of text such as in a tabular or array environment or in an equation environment.

The \\ command is a synonym for \newline (see \newline) under ordinary circumstances (an example of an exception is the p{...} column in a tabular environment; see tabular).

The \\ command is a macro, and its definition changes by context so that its definition in normal text, a center environment, a flushleft environment, and a tabular are all different. In normal text when it forces a linebreak it is essentially a shorthand for \newline.  It does not end horizontal mode or end the paragraph, it just inserts some glue and penalties so that when the paragraph does end a linebreak will occur at that point, with the short line padded with white space.

You get LaTeX Error: There's no line here to end if you use \\ to ask for a new line, rather than to end the current line. An example is if you have \begin{document}\\ or, more likely, something like this.

     \begin{center}
       \begin{minipage}{0.5\textwidth}
       \\
       In that vertical space put your mark.
       \end{minipage}
     \end{center}

Fix it by replacing the double backslash with something like \vspace{\baselineskip}.

\obeycr & \restorecr
====================

The \obeycr command makes a return in the input file (^^M, internally) the same as \\, followed by \relax.  So each new line in the input will also be a new line in the output.  The \restorecr command restores normal line-breaking behavior.

This is not the way to show verbatim text or computer code. See verbatim instead.

With LaTeX's usual defaults, this

     aaa
     bbb

     \obeycr
     ccc
     ddd
        eee

     \restorecr
     fff
     ggg

     hhh
     iii

produces output like this.

       aaa bbb
       ccc
     ddd
     eee

     fff ggg
       hhh iii

The indents are paragraph indents.

\newline
========

In ordinary text, this ends a line in a way that does not right-justify the line, so the prior text is not stretched. That is, in paragraph mode (see Modes), the \newline command is equivalent to double-backslash (see \\).  This command is fragile (see \protect).

However, the two commands are different inside a tabular or array environment. In a column with a specifier producing a paragraph box such as typically p{...}, \newline will insert a line end inside of the column; that is, it does not break the entire tabular row.  To break the entire row use \\ or its equivalent \tabularnewline.

This will print Name: and Address: as two lines in a single cell of the table.

     \begin{tabular}{p{1in}{\hspace{2in}}p{1in}}
       Name: \newline Address: &Date: \\ \hline
     \end{tabular}

The Date: will be baseline-aligned with Name:.

\- (discretionary hyphen)
=========================

Tell LaTeX that it may hyphenate the word at that point.  When you insert \- commands in a word, the word will only be hyphenated at those points and not at any of the hyphenation points that LaTeX might otherwise have chosen.  This command is robust (see \protect).

LaTeX is good at hyphenating and usually finds most of the correct hyphenation points, while almost never using an incorrect one.  The \- command is for exceptional cases.

For example, LaTeX does not ordinarily hyphenate words containing a hyphen.  Below, the long and hyphenated word means LaTeX has to put in unacceptably large spaces to set the narrow column.

     \begin{tabular}{rp{1.75in}}
       Isaac Asimov &The strain of
                    anti-intellectualism
                    % an\-ti-in\-tel\-lec\-tu\-al\-ism
                    has been a constant thread winding its way through our
                    political and cultural life, nurtured by
                    the false notion that democracy means that
                    `my ignorance is just as good as your knowledge'.
     \end{tabular}

Commenting out the third line and uncommenting the fourth makes a much better fit.

The \- command only allows LaTeX to break there, it does not require that it break there.  You can insist on a split with something like Hef-\linebreak feron.  Of course, if you later change the text then this forced break may look very odd, so this approach requires care.

\discretionary (generalized hyphenation point)
==============================================

Synopsis:

     \discretionary{PRE-BREAK}{POST-BREAK}{NO-BREAK}

Handle word changes around hyphens.  This command is not often used in LaTeX documents.

If a line break occurs at the point where \discretionary appears then TeX puts PRE-BREAK at the end of the current line and puts POST-BREAK at the start of the next line.  If there is no line break here then TeX puts NO-BREAK

In difficult the three letters ffi form a ligature.  But TeX can nonetheless break between the two f's with this.

     di\discretionary{f-}{fi}{ffi}cult

Note that users do not have to do this.  It is typically handled automatically by TeX's hyphenation algorithm.

\fussy & \sloppy
================

Declarations to make TeX more picky or less picky about line breaking.  Declaring \fussy usually avoids too much space between words, at the cost of an occasional overfull box.  Conversely, \sloppy avoids overfull boxes while suffering loose interword spacing.

The default is \fussy.  Line breaking in a paragraph is controlled by whichever declaration is current at the blank line, or \par, or displayed equation ending that paragraph.  So to affect the line breaks, include that paragraph-ending material in the scope of the command.

sloppypar
---------

Synopsis:

     \begin{sloppypar}
       ... paragraphs ...
     \end{sloppypar}

Typeset the paragraphs with \sloppy in effect (see \fussy & \sloppy).  Use this to locally adjust line breaking, to avoid Overfull box or Underfull box errors.

The example is simple.

     \begin{sloppypar}
       Her plan for the morning thus settled, she sat quietly down to her
       book after breakfast, resolving to remain in the same place and the
       same employment till the clock struck one; and from habitude very
       little incommoded by the remarks and ejaculations of Mrs.\ Allen,
       whose vacancy of mind and incapacity for thinking were such, that
       as she never talked a great deal, so she could never be entirely
       silent; and, therefore, while she sat at her work, if she lost her
       needle or broke her thread, if she heard a carriage in the street,
       or saw a speck upon her gown, she must observe it aloud, whether
       there were anyone at leisure to answer her or not.
     \end{sloppypar}

\hyphenation
============

Synopsis:

     \hyphenation{WORD1 ...}

Declares allowed hyphenation points within the words in the list.  The words in that list are separated by spaces.  Show permitted points for hyphenation with a dash character, -.

Here is an example:

     \hyphenation{hat-er il-lit-e-ra-ti tru-th-i-ness}

Use lowercase letters.  TeX will only hyphenate if the word matches exactly.  Multiple \hyphenation commands accumulate.

\linebreak & \nolinebreak
=========================

Synopses, one of:

     \linebreak
     \linebreak[ZERO-TO-FOUR]

or one of these.

     \nolinebreak
     \nolinebreak[ZERO-TO-FOUR]

Encourage or discourage a line break.  The optional ZERO-TO-FOUR is an integer that allows you to soften the instruction.  The default is 4, so that without the optional argument these commands entirely force or prevent the break.  But for instance, \nolinebreak[1] is a suggestion that another place may be better.  The higher the number, the more insistent the request.  Both commands are fragile (see \protect).

Here we tell LaTeX that a good place to put a linebreak is after the standard legal text.

     \boilerplatelegal{} \linebreak[2]
     We especially encourage applications from members of traditionally
     underrepresented groups.

When you issue \linebreak, the spaces in the line are stretched out so that it extends to the right margin.  See \\ and \newline to have the spaces not stretched out.

Page breaking
*************

Ordinarily LaTeX automatically takes care of breaking output into pages with its usual aplomb.  But if you are writing commands, or tweaking the final version of a document, then you may need to understand how to influence its actions.

LaTeX's algorithm for splitting a document into pages is more complex than just waiting until there is enough material to fill a page and outputting the result.  Instead, LaTeX typesets more material than would fit on the page and then chooses a break that is optimal in some way (it has the smallest badness). An example of the advantage of this approach is that if the page has some vertical space that can be stretched or shrunk, such as with rubber lengths between paragraphs, then LaTeX can use that to avoid widow lines (where a new page starts with the last line of a paragraph; LaTeX can squeeze the extra line onto the first page) and orphans (where the first line of paragraph is at the end of a page; LaTeX can stretch the material of the first page so the extra line falls on the second page). Another example is where LaTeX uses available vertical shrinkage to fit on a page not just the header for a new section but also the first two lines of that section.

But LaTeX does not optimize over the entire document's set of page breaks. So it can happen that the first page break is great but the second one is lousy; to break the current page LaTeX doesn't look as far ahead as the next page break.  So occasionally you may want to influence page breaks while preparing a final version of a document.

See Layout for more material that is relevant to page breaking.

\clearpage & \cleardoublepage
=============================

Synopsis:

     \clearpage

or

     \cleardoublepage

End the current page and output all of the pending floating figures and tables (see Floats).  If there are too many floats to fit on the page then LaTeX will put in extra pages containing only floats.  In two-sided printing, \cleardoublepage also makes the next page of content a right-hand page, an odd-numbered page, if necessary inserting a blank page.  The \clearpage command is robust while \cleardoublepage is fragile (see \protect).

LaTeX's page breaks are optimized so ordinarily you only use this command in a document body to polish the final version, or inside commands.

The \cleardoublepage command will put in a blank page, but it will have the running headers and footers.  To get a really blank page, use this command.

     \let\origdoublepage\cleardoublepage
     \newcommand{\clearemptydoublepage}{%
       \clearpage
       {\pagestyle{empty}\origdoublepage}%
     }

If you want LaTeX's standard \chapter command to do this then add the line \let\cleardoublepage\clearemptydoublepage.

The command \newpage (see \newpage) also ends the current page, but without clearing pending floats.  And, if LaTeX is in two-column mode then \newpage ends the current column while \clearpage and \cleardoublepage end the current page.

\newpage
========

Synopsis:

     \newpage

End the current page.  This command is robust (see \protect).

LaTeX's page breaks are optimized so ordinarily you only use this command in a document body to polish the final version, or inside commands.

While the commands \clearpage and \cleardoublepage also end the current page, in addition they clear pending floats (see \clearpage & \cleardoublepage).  And, if LaTeX is in two-column mode then \clearpage and \cleardoublepage end the current page, possibly leaving an empty column, while \newpage only ends the current column.

In contrast with \pagebreak (see \pagebreak & \nopagebreak), the \newpage command will cause the new page to start right where requested.  This

     Four score and seven years ago our fathers brought forth on this
     continent,
     \newpage
     \noindent a new nation, conceived in Liberty, and dedicated to the
     proposition that all men are created equal.

makes a new page start after continent, and the cut-off line is not right justified.  In addition, \newpage does not vertically stretch out the page, as \pagebreak does.

\enlargethispage
================

Synopsis, one of:

     \enlargethispage{size}
     \enlargethispage*{size}

Enlarge the \textheight for the current page.  The required argument SIZE must be a rigid length (see Lengths).  It may be positive or negative.  This command is fragile (see \protect).

A common strategy is to wait until you have the final text of a document, and then pass through it tweaking line and page breaks.  This command allows you some page size leeway.

This will allow one extra line on the current page.

     \enlargethispage{\baselineskip}

The starred form \enlargesthispage* tries to squeeze the material together on the page as much as possible, for the common use case of getting one more line on the page. This is often used together with an explicit \pagebreak.

\pagebreak & \nopagebreak
=========================

Synopses:

     \pagebreak
     \pagebreak[ZERO-TO-FOUR]

or

     \nopagebreak
     \nopagebreak[ZERO-TO-FOUR]

Encourage or discourage a page break.  The optional ZERO-TO-FOUR is an integer that allows you to soften the request. The default is 4, so that without the optional argument these commands entirely force or prevent the break.  But for instance \nopagebreak[1] suggests to LaTeX that another spot might be preferable.  The higher the number, the more insistent the request.  Both commands are fragile (see \protect).

LaTeX's page endings are optimized so ordinarily you only use this command in a document body to polish the final version, or inside commands.

If you use these inside a paragraph, they apply to the point following the line in which they appear.  So this

     Four score and seven years ago our fathers brought forth on this
     continent,
     \pagebreak
     a new nation, conceived in Liberty, and dedicated to the proposition
     that all men are created equal.

does not give a page break at continent, but instead at nation, since that is where LaTeX breaks that line.  In addition, with \pagebreak the vertical space on the page is stretched out where possible so that it extends to the normal bottom margin.  This can look strange, and if \flushbottom is in effect this can cause you to get Underfull \vbox (badness 10000) has occurred while \output is active.  See \newpage for a command that does not have these effects.

Footnotes
*********

Place a footnote at the bottom of the current page, as here.

     Noël Coward quipped that having to read a footnote is like having
     to go downstairs to answer the door, while in the midst of making
     love.\footnote{%
       I wouldn't know, I don't read footnotes.}

You can put multiple footnotes on a page. If the footnote text becomes too long then it will flow to the next page.

You can also produce footnotes by combining the \footnotemark and the \footnotetext commands, which is useful in special circumstances.

To make bibliographic references come out as footnotes you need to include a bibliographic style with that behavior (see Using BibTeX).

\footnote
=========

Synopsis, one of:

     \footnote{TEXT}
     \footnote[NUMBER]{TEXT}

Place a footnote TEXT at the bottom of the current page.

     There are over a thousand footnotes in Gibbon's
     \textit{Decline and Fall of the Roman Empire}.\footnote{%
       After reading an early version with endnotes David Hume complained,
       ``One is also plagued with his Notes, according to the present Method
       of printing the Book'' and suggested that they ``only to be printed
       at the Margin or the Bottom of the Page.''}

The optional argument NUMBER allows you to specify the number of the footnote.  If you use this then LaTeX does not increment the footnote counter.

By default, LaTeX uses arabic numbers as footnote markers.  Change this with something like \renewcommand{\thefootnote}{\fnsymbol{footnote}}, which uses a sequence of symbols (see \alph \Alph \arabic \roman \Roman \fnsymbol).  To make this change global put that in the preamble.  If you make the change local then you may want to reset the counter with \setcounter{footnote}{0}.

LaTeX determines the spacing of footnotes with two parameters.

\footnoterule
     Produces the rule separating the main text on a page from the page's footnotes.  Default dimensions in the standard document classes (except slides, where it does not appear) is: vertical thickness of 0.4pt, and horizontal size of 0.4\columnwidth long. Change the rule with something like this.

          \renewcommand{\footnoterule}{% Kerns avoid vertical space
            \kern -3pt                         % This -3 is negative
            \hrule width \textwidth height 1pt % of the sum of this 1
            \kern 2pt}                         % and this 2

\footnotesep
     The height of the strut placed at the beginning of the footnote (see \strut).  By default, this is set to the normal strut for \footnotesize fonts (see Font sizes), therefore there is no extra space between footnotes.  This is 6.65pt for 10pt, 7.7pt for 11pt, and 8.4pt for 12pt.  Change it as with \setlength{\footnotesep}{11pt}.

The \footnote command is fragile (see \protect).

LaTeX's default puts many restrictions on where you can use a \footnote; for instance, you cannot use it in an argument to a sectioning command such as \chapter (it can only be used in outer paragraph mode; see Modes).  There are some workarounds; see following sections.

In a minipage environment the \footnote command uses the mpfootnote counter instead of the footnote counter, so they are numbered independently.  They are shown at the bottom of the environment, not at the bottom of the page.  And by default they are shown alphabetically. See minipage and Footnotes in a table.

\footnotemark
=============

Synopsis, one of:

     \footnotemark
     \footnotemark[NUMBER]

Put the current footnote mark in the text. To specify associated text for the footnote see \footnotetext.  The optional argument NUMBER causes the command to use that number to determine the footnote mark. This command can be used in inner paragraph mode (see Modes).

If you use \footnotemark without the optional argument then it increments the footnote counter but if you use the optional NUMBER then it does not. The next example produces several consecutive footnote markers referring to the same footnote.

     The first theorem\footnote{Due to Gauss.}
     and the second theorem\footnotemark[\value{footnote}]
     and the third theorem.\footnotemark[\value{footnote}]

If there are intervening footnotes then you must remember the value of the common mark.  This example gives the same institutional affiliation to both the first and third authors (\thanks is a version of footnote), by-hand giving the number of the footnote.

     \title{A Treatise on the Binomial Theorem}
     \author{J Moriarty\thanks{University of Leeds}
       \and A C Doyle\thanks{Durham University}
       \and S Holmes\footnotemark[1]}
     \begin{document}
     \maketitle

This uses a counter to remember the footnote number.  The third sentence is followed by the same footnote marker as the first.

     \newcounter{footnoteValueSaver}
     All babies are illogical.\footnote{%
       Lewis Carroll.}\setcounter{footnoteValueSaver}{\value{footnote}}
     Nobody is despised who can manage a crocodile.\footnote{%
       Captain Hook.}
     Illogical persons are despised.\footnotemark[\value{footnoteValueSaver}]
     Therefore, anyone who can manage a crocodile is not a baby.

This example accomplishes the same by using the package cleveref.

     \usepackage{cleveref}[2012/02/15]   % in preamble
     \crefformat{footnote}{#2\footnotemark[#1]#3}
     ...
     The theorem is from Evers.\footnote{\label{fn:TE}Tinker, Evers, 1994.}
     The corollary is from Chance.\footnote{Evers, Chance, 1990.}
     But the key lemma is from Tinker.\cref{fn:TE}

It will work with the package hyperref.

\footnotetext
=============

Synopsis, one of:

     \footnotetext{TEXT}
     \footnotetext[NUMBER]{TEXT}

Place TEXT at the bottom of the page as a footnote.  It pairs with \footnotemark (see \footnotemark) and can come anywhere after that command, but must appear in outer paragraph mode (see Modes). The optional argument NUMBER changes the number of the footnote mark.

See \footnotemark and Footnotes in a table for usage examples.

Footnotes in section headings
=============================

Putting a footnote in a section heading, as in:

     \section{Full sets\protect\footnote{This material due to ...}}

causes the footnote to appear at the bottom of the page where the section starts, as usual, but also at the bottom of the table of contents, where it is not likely to be desired.  The simplest way to have it not appear on the table of contents is to use the optional argument to \section

     \section[Please]{Please\footnote{%
       Don't footnote in chapter and section headers!}}

No \protect is needed in front of \footnote here because what gets moved to the table of contents is the optional argument.

Footnotes in a table
====================

Inside a tabular or array environment the \footnote command does not work; there is a footnote mark in the table cell but the footnote text does not appear.  The solution is to use a minipage environment as here (see minipage).

     \begin{center}
       \begin{minipage}{\textwidth} \centering
          \begin{tabular}{l|l}
            \textsc{Ship}           &\textsc{Book} \\ \hline
            \textit{HMS Sophie}     &Master and Commander  \\
            \textit{HMS Polychrest} &Post Captain  \\
            \textit{HMS Lively}     &Post Captain \\
            \textit{HMS Surprise}   &A number of books\footnote{%
                                       Starting with HMS Surprise.}
          \end{tabular}
       \end{minipage}
     \end{center}

Inside a minipage, footnote marks are lowercase letters.  Change that with something like \renewcommand{\thempfootnote}{\arabic{mpfootnote}} (see \alph \Alph \arabic \roman \Roman \fnsymbol).

The footnotes in the prior example appear at the bottom of the minipage.  To have them appear at the bottom of the main page, as part of the regular footnote sequence, use the \footnotemark and \footnotetext pair and make a new counter.

     \newcounter{mpFootnoteValueSaver}
     \begin{center}
       \begin{minipage}{\textwidth}
         \setcounter{mpFootnoteValueSaver}{\value{footnote}} \centering
          \begin{tabular}{l|l}
            \textsc{Woman}             &\textsc{Relationship} \\ \hline
            Mona                       &Attached\footnotemark  \\
            Diana Villiers             &Eventual wife  \\
            Christine Hatherleigh Wood &Fiance\footnotemark
          \end{tabular}
       \end{minipage}%  percent sign keeps footnote text close to minipage
       \stepcounter{mpFootnoteValueSaver}%
         \footnotetext[\value{mpFootnoteValueSaver}]{%
           Little is known other than her death.}%
       \stepcounter{mpFootnoteValueSaver}%
         \footnotetext[\value{mpFootnoteValueSaver}]{%
           Relationship is unresolved in XXI.}
     \end{center}

For a floating table environment (see table), use the tablefootnote package.

     \usepackage{tablefootnote}  % in preamble
        ...
     \begin{table}
       \centering
          \begin{tabular}{l|l}
          \textsc{Date}  &\textsc{Campaign} \\ \hline
          1862           &Fort Donelson \\
          1863           &Vicksburg     \\
          1865           &Army of Northern Virginia\tablefootnote{%
                           Ending the war.}
          \end{tabular}
         \caption{Forces captured by US Grant}
     \end{table}

The footnote appears at the page bottom and is numbered in sequence with other footnotes.

Footnotes of footnotes
======================

Particularly in the humanities, authors can have multiple classes of footnotes, including having footnotes of footnotes.  The package bigfoot extends LaTeX's default footnote mechanism in many ways, including allow these two, as in this example.

     \usepackage{bigfoot}    % in preamble
     \DeclareNewFootnote{Default}
     \DeclareNewFootnote{from}[alph]   % create class \footnotefrom{}
      ...
     The third theorem is a partial converse of the
     second.\footnotefrom{%
       First noted in Wilson.\footnote{Second edition only.}}

Definitions
***********

LaTeX has support for making new commands of many different kinds.

\newcommand & \renewcommand
===========================

Synopses, one of:

     \newcommand{\CMD}{DEFN}
     \newcommand{\CMD}[NARGS]{DEFN}
     \newcommand{\CMD}[NARGS][OPTARGDEFAULT]{DEFN}
     \newcommand*{\CMD}{DEFN}
     \newcommand*{\CMD}[NARGS]{DEFN}
     \newcommand*{\CMD}[NARGS][OPTARGDEFAULT]{DEFN}

or one of these.

     \renewcommand{\CMD}[NARGS]{DEFN}
     \renewcommand{\CMD}[NARGS]{DEFN}
     \renewcommand{\CMD}[NARGS][OPTARGDEFAULT]{DEFN}
     \renewcommand*{\CMD}{DEFN}
     \renewcommand*{\CMD}[NARGS]{DEFN}
     \renewcommand*{\CMD}[NARGS][OPTARGDEFAULT]{DEFN}

Define or redefine a command.  See also the discussion of \DeclareRobustCommand in Class and package commands. The starred form of these two requires that the arguments not contain multiple paragraphs of text (in plain TeX terms that it not be \long).

These are the parameters:

cmd

     Required; the command name.  It must begin with a backslash, \, and must not begin with the four letter string \end.  For \newcommand, it must not be already defined.  For \renewcommand, this name must already be defined.

nargs
     Optional; an integer from 0 to 9, specifying the number of arguments that the command takes, including any optional argument.  Omitting this argument is the same as specifying 0, meaning that the command has no arguments.  If you redefine a command, the new version can have a different number of arguments than the old version.

optargdefault
     Optional; if this argument is present then the first argument of \CMD is optional, with default value OPTARGDEFAULT (which may be the empty string).  If this argument is not present then \CMD does not take an optional argument.

     That is, if \CMD is used with square brackets, as in \CMD[OPTVAL]{...}..., then within DEFN the parameter #1 is set to the value of OPTVAL.  On the other hand, if \CMD is called without the square brackets then within DEFN the parameter #1 is set to the value of OPTARGDEFAULT.  In either case, the required arguments start with #2.

     Omitting [OPTARGDEFAULT] is different from having the square brackets with no contents, as in [].  The former sets #1 to the value of OPTARGDEFAULT; the latter sets #1 to the empty string.

defn
     Required; the text to be substituted for every occurrence of \CMD. The parameters #1, #2, ... #NARGS are replaced by the values that you supply when you call the command (or by the default value if there is an optional argument and you don't exercise the option).

TeX ignores spaces in the source following an alphabetic control sequence, as in \cmd .  If you actually want a space there, one solution is to type {} after the command (\cmd{} , and another solution is to use an explicit control space (\cmd\ ).

A simple example of defining a new command: \newcommand{\RS}{Robin Smith} results in \RS being replaced by the longer text.  Redefining an existing command is similar: \renewcommand{\qedsymbol}{{\small QED}}.

If you try to define a command and the name has already been used then you get something like LaTeX Error: Command \fred already defined. Or name \end... illegal, see p.192 of the manual.  If you try to redefine a command and the name has not yet been used then you get something like LaTeX Error: \hank undefined.

Here the first command definition has no arguments, and the second has one required argument.

     \newcommand{\student}{Ms~O'Leary}
     \newcommand{\defref}[1]{Definition~\ref{#1}}

Use the first as in I highly recommend \student{} to you.  The second has a variable, so that \defref{def:basis} expands to Definition~\ref{def:basis}, which ultimately expands to something like Definition~3.14.

Similarly, but with two required arguments: \newcommand{\nbym}[2]{$#1 \times #2$} is invoked as \nbym{2}{k}.

This example has an optional argument.

     \newcommand{\salutation}[1][Sir or Madam]{Dear #1:}

Then \salutation gives Dear Sir or Madam: while \salutation[John] gives Dear John:.  And \salutation[] gives Dear :.

This example has an optional argument and two required arguments.

     \newcommand{\lawyers}[3][company]{#2, #3, and~#1}
     I employ \lawyers[Howe]{Dewey}{Cheatem}.

The output is I employ Dewey, Cheatem, and Howe.  The optional argument, the Howe, is associated with #1, while Dewey and Cheatem are associated with #2 and #3.  Because of the optional argument, \lawyers{Dewey}{Cheatem} will give the output I employ Dewey, Cheatem, and company.

The braces around DEFN do not define a group, that is, they do not delimit the scope of the result of expanding DEFN.  For example, with \newcommand{\shipname}[1]{\it #1}, in this sentence,

     The \shipname{Monitor} met the \shipname{Merrimac}.

the words met the would incorrectly be in italics.  The solution is to put another pair of braces inside the definition: \newcommand{\shipname}[1]{{\it #1}}.

\providecommand
===============

Synopses, one of:

     \providecommand{CMD}{DEFN}
     \providecommand{CMD}[NARGS]{DEFN}
     \providecommand{CMD}[NARGS][OPTARGDEFAULT]{DEFN}
     \providecommand*{CMD}{DEFN}
     \providecommand*{CMD}[NARGS]{DEFN}
     \providecommand*{CMD}[NARGS][OPTARGDEFAULT]{DEFN}

Defines a command, as long as no command of this name already exists. If no command of this name already exists then this has the same effect as \newcommand.  If a command of this name already exists then this definition does nothing.  This is particularly useful in a file that may be loaded more than once, such as a style file. See \newcommand & \renewcommand for the description of the arguments.

This example

     \providecommand{\myaffiliation}{Saint Michael's College}
     \providecommand{\myaffiliation}{Saint Michael's College}
     From \myaffiliation.

outputs From Saint Michael's College.  Unlike \newcommand, the repeated use of \providecommand does not give an error.

\makeatletter & \makeatother
============================

Synopsis:

     \makeatletter
       ... definition of commands with @ in their name ..
     \makeatother

Use this pair when you redefine LaTeX commands that are named with an at-sign character @.  The \makeatletter declaration makes the at-sign character have the category code of a letter, code 11.  The \makeatother declaration sets the category code of the at-sign to code 12, its default value.

As TeX reads characters, it assigns each one a category code, or catcode. For instance, it assigns the backslash character \ the catcode 0.  Command names consist of a category 0 character, ordinarily backslash, followed by letters, category 11 characters (except that a command name can also consist of a category 0 character followed by a single non-letter symbol).

LaTeX's source code has the convention that some commands use @ in their name.  These commands are mainly intended for package or class writers.  The convention prevents authors who are just using a package or class from accidentally replacing such a command with one of their own, because by default the at-sign has catcode 12.

The pair \makeatletter and \makeatother changes the default code and then changes it back.  Use them inside a .tex file, in the preamble, when you are defining or redefining commands named with @, by having them surround your definition.  Don't use these inside .sty or .cls files since the \usepackage and \documentclass commands already arrange that the at-sign has the character code of a letter, catcode 11.

For a comprehensive list of macros with an at-sign in their names see http://ctan.org/pkg/macros2e.

In this example the class file has a command \thesis@universityname that the user wants to change.  These three lines should go in the preamble, before the \begin{document}.

     \makeatletter
     \renewcommand{\thesis@universityname}{Saint Michael's College}
     \makeatother

\@ifstar
========

Synopsis:

     \newcommand{\mycmd}{\@ifstar{\mycmd@star}{\mycmd@nostar}}
     \newcommand{\mycmd@nostar}[NOSTAR-NUM-ARGS]{NOSTAR-BODY}
     \newcommand{\mycmd@star}[STAR-NUM-ARGS]{STAR-BODY}

Many standard LaTeX environments or commands have a variant with the same name but ending with a star character *, an asterisk. Examples are the table and table* environments and the \section and \section* commands.

When defining environments, following this pattern is straightforward because \newenvironment and \renewenvironment allow the environment name to contain a star.  For commands the situation is more complex.  As in the synopsis above, there will be a user-called command, given above as \mycmd, which peeks ahead to see if it is followed by a star.  For instance, LaTeX does not really have a \section* command; instead, the \section command peeks ahead.  This command does not accept arguments but instead expands to one of two commands that do accept arguments.  In the synopsis these two are \mycmd@nostar and \mycmd@star.  They could take the same number of arguments or a different number, or no arguments at all. As always, in a LaTeX document a command using at-sign @ must be enclosed inside a \makeatletter ... \makeatother block (see \makeatletter & \makeatother).

This example of \@ifstar defines the command \ciel and a variant \ciel*.  Both have one required argument.  A call to \ciel{night} will return "starry night sky" while \ciel*{blue} will return "starry not blue sky".

     \newcommand*{\ciel@unstarred}[1]{starry #1 sky}
     \newcommand*{\ciel@starred}[1]{starry not #1 sky}
     \newcommand*{\ciel}{\@ifstar{\ciel@starred}{\ciel@unstarred}}

In the next example, the starred variant takes a different number of arguments than the unstarred one.  With this definition, Agent 007's ``My name is \agentsecret*{Bond}, \agentsecret{James}{Bond}.'' is equivalent to entering the commands ``My name is \textsc{Bond}, \textit{James} textsc{Bond}.''

     \newcommand*{\agentsecret@unstarred}[2]{\textit{#1} \textsc{#2}}
     \newcommand*{\agentsecret@starred}[1]{\textsc{#1}}
     \newcommand*{\agentsecret}{%
       \@ifstar{\agentsecret@starred}{\agentsecret@unstarred}}

There are two sometimes more convenient ways to accomplish the work of \@ifstar.  The suffix package allows the construct \newcommand\mycommand{UNSTARRED VERSION} followed by \WithSuffix\newcommand\mycommand*{STARRED VERSION}.  And LaTeX3 has the xparse package that allows this code.

     \NewDocumentCommand\foo{s}{\IfBooleanTF#1
       {STARRED VERSION}%
       {UNSTARRED VERSION}%
       }

\newcounter: Allocating a counter
=================================

Synopsis, one of:

     \newcounter{COUNTERNAME}
     \newcounter{COUNTERNAME}[SUPERCOUNTER]

Globally defines a new counter named COUNTERNAME and initialize it to zero (see Counters).

The name COUNTERNAME must consist of letters only. It does not begin with a backslash.  This name must not already be in use by another counter.

When you use the optional argument [SUPERCOUNTER] then the counter COUNTERNAME will be reset to zero whenever SUPERCOUNTER is incremented.  For example, ordinarily subsection is numbered within section so that any time you increment SECTION, either with \stepcounter (see \stepcounter) or \refstepcounter (see \refstepcounter), then LaTeX will reset SUBSECTION to zero.

This example

     \newcounter{asuper}  \setcounter{asuper}{1}
     \newcounter{asub}[asuper] \setcounter{asub}{3}   % Note `asuper'
     The value of asuper is \arabic{asuper} and of asub is \arabic{asub}.
     \stepcounter{asuper}
     Now asuper is \arabic{asuper} while asub is \arabic{asub}.

produces The value of asuper is 1 and that of asub is 3 and Now asuper is 2 while asub is 0.

If the counter already exists, for instance by entering asuper twice, then you get something like LaTeX Error: Command \c@asuper already defined.  Or name \end... illegal, see p.192 of the manual..

If you use the optional argument then the super counter must already exist. Entering \newcounter{jh}[lh] when lh is not a defined counter will get you LaTeX Error: No counter 'lh' defined.

\newlength
==========

Synopsis:

     \newlength{ARG}

Allocate a new length register (see Lengths).  The required argument ARG must begin with a backslash, \.  The new register holds rubber lengths such as 72.27pt or 1in plus.2in minus.1in (a LaTeX length register is what plain TeX calls a skip register).  The initial value is zero.  The control sequence \ARG must not be already defined.

An example:

     \newlength{\graphichgt}

If you forget the backslash then you get Missing control sequence inserted.  If the command sequence already exists then you get something like LaTeX Error: Command \graphichgt already defined. Or name \end... illegal, see p.192 of the manual.

\newsavebox
===========

Synopsis:

     \newsavebox{\CMD}

Define \CMD, the string consisting of a backslash followed by CMD, to refer to a new bin for storing material.  These bins hold material that has been typeset, to use multiple times or to measure or manipulate (see Boxes).  The bin name \CMD is required, must start with a backslash, \, and must not already be a defined command. This command is fragile (see \protect).

This allocates a bin and then puts typeset material into it.

     \newsavebox{\logobox}
     \savebox{\logobox}{LoGo}
     Our logo is \usebox{\logobox}.

The output is Our logo is LoGo.

If there is an already defined bin then you get something like LaTeX Error: Command \logobox already defined. Or name \end... illegal, see p.192 of the manual.

The allocation of a box is global.

\newenvironment & \renewenvironment
===================================

Synopses, one of:

     \newenvironment{ENV}{BEGDEF}{ENDDEF}
     \newenvironment{ENV}[NARGS]{BEGDEF}{ENDDEF}
     \newenvironment{ENV}[NARGS][OPTARGDEFAULT]{BEGDEF}{ENDDEF}
     \newenvironment*{ENV}{BEGDEF}{ENDDEF}
     \newenvironment*{ENV}[NARGS]{BEGDEF}{ENDDEF}
     \newenvironment*{ENV}[NARGS][OPTARGDEFAULT]{BEGDEF}{ENDDEF}

or one of these.

     \renewenvironment{ENV}{BEGDEF}{ENDDEF}
     \renewenvironment{ENV}[NARGS]{BEGDEF}{ENDDEF}
     \renewenvironment{ENV}[NARGS][OPTARGDEFAULT]{BEGDEF}{ENDDEF}
     \renewenvironment*{ENV}{BEGDEF}{ENDDEF}
     \renewenvironment*{ENV}[NARGS]{BEGDEF}{ENDDEF}
     \renewenvironment*{ENV}[NARGS][OPTARGDEFAULT]{BEGDEF}{ENDDEF}

Define or redefine the environment ENV, that is, create the construct \begin{ENV} ... BODY ... \end{ENV}.

The starred form of these commands requires that the arguments not contain multiple paragraphs of text.  However, the body of these environments can contain multiple paragraphs.

env
     Required; the environment name.  It consists only of letters or the * character, and thus does not begin with backslash, \. It must not begin with the string end.  For \newenvironment, the name ENV must not be the name of an already existing environment, and also the command \ENV must be undefined.  For \renewenvironment, ENV must be the name of an existing environment.

nargs
     Optional; an integer from 0 to 9 denoting the number of arguments of that the environment takes.  When you use the environment these arguments appear after the \begin, as in \begin{ENV}{ARG1} ... {ARGN}.  Omitting this is equivalent to setting it to 0; the environment will have no arguments.  When redefining an environment, the new version can have a different number of arguments than the old version.

optargdefault
     Optional; if this is present then the first argument of the defined environment is optional, with default value OPTARGDEFAULT (which may be the empty string).  If this is not in the definition then the environment does not take an optional argument.

     That is, when OPTARGDEFAULT is present in the definition of the environment then you can start the environment with square brackets, as in \begin{ENV}[OPTVAL]{...} ... \end{ENV}. In this case, within BEGDEFN the parameter #1 is set to the value of OPTVAL.  If you call \begin{ENV} without square brackets, then within BEGDEFN the parameter #1 is set to the value of the default OPTARGDEFAULT.  In either case, any required arguments start with #2.

     Omitting [MYVAL] in the call is different than having the square brackets with no contents, as in [].  The former results in #1 expanding to OPTARGDEFAULT; the latter results in #1 expanding to the empty string.

begdef
     Required; the text expanded at every occurrence of \begin{ENV}.  Within BEGDEF, the parameters #1, #2, ... #NARGS, are replaced by the values that you supply when you call the environment; see the examples below.

enddef
     Required; the text expanded at every occurrence of \end{ENV}.  This may not contain any parameters, that is, you cannot use #1, #2, etc., here (but see the final example below).

All environments, that is to say the BEGDEF code, the environment body, and the ENDDEF code, are processed within a group.  Thus, in the first example below, the effect of the \small is limited to the quote and does not extend to material following the environment.

If you try to define an environment and the name has already been used then you get something like LaTeX Error: Command \fred already defined. Or name \end... illegal, see p.192 of the manual.  If you try to redefine an environment and the name has not yet been used then you get something like LaTeX Error: Environment hank undefined..

This example gives an environment like LaTeX's quotation except that it will be set in smaller type.

     \newenvironment{smallquote}{%
       \small\begin{quotation}
     }{%
       \end{quotation}
     }

This has an argument, which is set in boldface at the start of a paragraph.

     \newenvironment{point}[1]{%
       \noindent\textbf{#1}
     }{%
     }

This one shows the use of a optional argument; it gives a quotation environment that cites the author.

     \newenvironment{citequote}[1][Shakespeare]{%
       \begin{quotation}
       \noindent\textit{#1}:
     }{%
       \end{quotation}
     }

The author's name is optional, and defaults to Shakespeare.  In the document, use the environment like this.

     \begin{citequote}[Lincoln]
       ...
     \end{citequote}

The final example shows how to save the value of an argument to use in ENDDEF, in this case in a box (see \sbox & \savebox).

     \newsavebox{\quoteauthor}
     \newenvironment{citequote}[1][Shakespeare]{%
       \sbox\quoteauthor{#1}%
       \begin{quotation}
     }{%
       \hspace{1em plus 1fill}---\usebox{\quoteauthor}
       \end{quotation}
     }

\newtheorem
===========

Synopses:

     \newtheorem{NAME}{TITLE}
     \newtheorem{NAME}{TITLE}[NUMBERED_WITHIN]
     \newtheorem{NAME}[NUMBERED_LIKE]{TITLE}

Define a new theorem-like environment.  You can specify one of NUMBERED_WITHIN and NUMBERED_LIKE, or neither, but not both.

The first form, \newtheorem{NAME}{TITLE}, creates an environment that will be labelled with TITLE; see the first example below.

The second form, \newtheorem{NAME}{TITLE}[NUMBERED_WITHIN], creates an environment whose counter is subordinate to the existing counter NUMBERED_WITHIN, so this counter will be reset when NUMBERED_WITHIN is reset.  See the second example below.

The third form \newtheorem{NAME}[NUMBERED_LIKE]{TITLE}, with optional argument between the two required arguments, creates an environment whose counter will share the previously defined counter NUMBERED_LIKE.  See the third example.

This command creates a counter named NAME.  In addition, unless the optional argument NUMBERED_LIKE is used, inside of the theorem-like environment the current \ref value will be that of \theNUMBERED_WITHIN (see \ref).

This declaration is global.  It is fragile (see \protect).

Arguments:

name
     The name of the environment.  It is a string of letters.  It must not begin with a backslash, \.  It must not be the name of an existing environment, and the command name \NAME must not already be defined.

title
     The text to be printed at the beginning of the environment, before the number. For example, Theorem.

numbered_within
     Optional; the name of an already defined counter, usually a sectional unit such as chapter or section.  When the NUMBERED_WITHIN counter is reset then the NAME environment's counter will also be reset.

     If this optional argument is not used then the command \theNAME is set to \arabic{NAME}.

numbered_like
     Optional; the name of an already defined theorem-like environment. The new environment will be numbered in sequence with NUMBERED_LIKE.

Without any optional arguments the environments are numbered sequentially.  The example below has a declaration in the preamble that results in Definition 1 and Definition 2 in the output.

     \newtheorem{defn}{Definition}
     \begin{document}
     \section{...}
     \begin{defn}
       First def
     \end{defn}

     \section{...}
     \begin{defn}
       Second def
     \end{defn}

This example has the same document body as the prior one.  But here \newtheorem's optional argument NUMBERED_WITHIN is given as section, so the output is like Definition 1.1 and Definition 2.1.

     \newtheorem{defn}{Definition}[section]
     \begin{document}
     \section{...}
     \begin{defn}
       First def
     \end{defn}

     \section{...}
     \begin{defn}
       Second def
     \end{defn}

In the next example there are two declarations in the preamble, the second of which calls for the new thm environment to use the same counter as defn.  It gives Definition 1.1, followed by Theorem 2.1 and Definition 2.2.

     \newtheorem{defn}{Definition}[section]
     \newtheorem{thm}[defn]{Theorem}
     \begin{document}
     \section{...}
     \begin{defn}
       First def
     \end{defn}

     \section{...}
     \begin{thm}
       First thm
     \end{thm}

     \begin{defn}
       Second def
     \end{defn}

\newfont
========

This command is obsolete. This description is here only to help with old documents.  New documents should define fonts in families through the New Font Selection Scheme which allows you to, for example, associate a boldface with a roman (see Fonts).

Synopsis:

     \newfont{\CMD}{FONT DESCRIPTION}

Define a command \CMD that will change the current font. The control sequence must not already be defined. It must begin with a backslash, \.

The FONT DESCRIPTION consists of a FONTNAME and an optional at clause.  LaTeX will look on your system for a file named FONTNAME.tfm.  The at clause can have the form either at DIMEN or scaled FACTOR, where a FACTOR of 1000 means no scaling.  For LaTeX's purposes, all this does is scale all the character and other font dimensions relative to the font's design size, which is a value defined in the .tfm file.

This defines two equivalent fonts and typesets a few characters in each.

     \newfont{\testfontat}{cmb10 at 11pt}
     \newfont{\testfontscaled}{cmb10 scaled 1100}
     \testfontat abc
     \testfontscaled abc

\protect
========

All LaTeX commands are either fragile or robust.  A fragile command can break when it is used in the argument to certain other commands.  Commands that contain data that LaTeX writes to an auxiliary file and re-reads later are fragile.  This includes material that goes into a table of contents, list of figures, list of tables, etc.  Fragile commands also include line breaks, any command that has an optional argument, and many more. To prevent such commands from breaking, one solution is to preceded them with the command \protect.

For example, when LaTeX runs the \section{SECTION NAME} command it writes the SECTION NAME text to the .aux auxiliary file, moving it there for use elsewhere in the document such as in the table of contents.  Any argument that is internally expanded by LaTeX without typesetting it directly is referred to as a moving argument.  A command is fragile if it can expand during this process into invalid TeX code.  Some examples of moving arguments are those that appear in the \caption{...} command (see figure), in the \thanks{...} command (see \maketitle), and in @-expressions in the tabular and array environments (see tabular).

If you get strange errors from commands used in moving arguments, try preceding it with \protect.  Every fragile commands must be protected with their own \protect.

Although usually a \protect command doesn't hurt, length commands are robust and should not be preceded by a \protect command. Nor can a \protect command be used in the argument to \addtocounter or \setcounter command.

In this example the \caption command gives a mysterious error about an extra curly brace.  Fix the problem by preceding each \raisebox command with \protect.

     \begin{figure}
       ...
       \caption{Company headquarters of A\raisebox{1pt}{B}\raisebox{-1pt}{C}}
     \end{figure}

In the next example the \tableofcontents command gives an error because the \(..\) in the section title expands to illegal TeX in the .toc file.  You can solve this by changing \(..\) to \protect\(..\protect\).

     \begin{document}
     \tableofcontents
     ...
     \section{Einstein's \( e=mc^2 \)}
     ...

\ignorespaces & \ignorespacesafterend
=====================================

Synopsis:

     \ignorespaces

or

     \ignorespacesafterend

Both commands cause LaTeX to ignore spaces after the end of the command up until the first non-space character.  The first is a command from Plain TeX, and the second is LaTeX-specific.

The ignorespaces is often used when defining commands via \newcommand, or \newenvironment, or \def.  The example below illustrates.  It allows a user to show the points values for quiz questions in the margin but it is inconvenient because, as shown in the enumerate list, users must not put any space between the command and the question text.

     \newcommand{\points}[1]{\makebox[0pt]{\makebox[10em][l]{#1~pts}}
     \begin{enumerate}
       \item\points{10}no extra space output here
       \item\points{15} extra space between the number and the `extra'
     \end{enumerate}

The solution is to change to this.

     \newcommand{\points}[1]{%
       \makebox[0pt]{\makebox[10em][l]{#1~pts}}\ignorespaces}

A second example shows spaces being removed from the front of text.  The commands below allow a user to uniformly attach a title to names.  But, as given, if a title accidentally starts with a space then \fullname will reproduce that.

     \makeatletter
     \newcommand{\honorific}[1]{\def\@honorific{#1}} % remember title
     \newcommand{\fullname}[1]{\@honorific~#1}       % put title before name
     \makeatother
     \begin{tabular}{|l|}
     \honorific{Mr/Ms}  \fullname{Jones} \\  % no extra space here
     \honorific{ Mr/Ms} \fullname{Jones}     % extra space before title
     \end{tabular}

To fix this, change to \newcommand{\fullname}[1]{\ignorespaces\@honorific~#1}.

The \ignorespaces is also often used in a \newenvironment at the end of the BEGIN clause, that is, as part of the second argument, as in \begin{newenvironment}{ENV NAME}{... \ignorespaces}{...}.

To strip spaces off the end of an environment use \ignorespacesafterend.  An example is that this will show a much larger vertical space between the first and second environments than between the second and third.

     \newenvironment{eq}{\begin{equation}}{\end{equation}}
     \begin{eq}
     e=mc^2
     \end{eq}
     \begin{equation}
     F=ma
     \end{equation}
     \begin{equation}
     E=IR
     \end{equation}

Putting a comment character % immediately after the \end{eq} will make the vertical space disappear, but that is inconvenient.  The solution is to change to \newenvironment{eq}{\begin{equation}}{\end{equation}\ignorespacesafterend}.

Counters
********

Everything LaTeX numbers for you has a counter associated with it. The name of the counter is often the same as the name of the environment or command associated with the number, except that the counter's name has no backslash \.  Thus, associated with the \chapter command is the chapter counter that keeps track of the chapter number.

Below is a list of the counters used in LaTeX's standard document classes to control numbering.

     part            paragraph       figure          enumi
     chapter         subparagraph    table           enumii
     section         page            footnote        enumiii
     subsection      equation        mpfootnote      enumiv
     subsubsection

The mpfootnote counter is used by the \footnote command inside of a minipage (see minipage).  The counters enumi through enumiv are used in the enumerate environment, for up to four levels of nesting (see enumerate).

Counters can have any integer value but they are typically positive.

New counters are created with \newcounter.  See \newcounter.

\alph \Alph \arabic \roman \Roman \fnsymbol: Printing counters
==============================================================

Print the value of a counter, in a specified style.  For instance, if the counter COUNTER has the value 1 then a \alph{COUNTER} in your source will result in a lowercase letter a appearing in the output.

All of these commands take a single counter as an argument, for instance, \alph{enumi}.  Note that the counter name does not start with a backslash.

\alph{COUNTER}
     Print the value of COUNTER in lowercase letters: `a', `b', ... If the counter's value is less than 1 or more than 26 then you get LaTeX Error: Counter too large.

\Alph{COUNTER}
     Print in uppercase letters: `A', `B', ... If the counter's value is less than 1 or more than 26 then you get LaTeX Error: Counter too large.

\arabic{COUNTER}
     Print in Arabic numbers such as 5 or -2.

\roman{COUNTER}
     Print in lowercase roman numerals: `i', `ii', ... If the counter's value is less than 1 then you get no warning or error but LaTeX does not print anything in the output.

\Roman{COUNTER}
     Print in uppercase roman numerals: `I', `II', ... If the counter's value is less than 1 then you get no warning or error but LaTeX does not print anything in the output.

\fnsymbol{COUNTER}
     Prints the value of COUNTER using a sequence of nine symbols that are traditionally used for labeling footnotes.  The value of COUNTER should be between 1 and 9, inclusive.  If the counter's value is less than 0 or more than 9 then you get LaTeX Error: Counter too large, while if it is 0 then you get no error or warning but LaTeX does not output anything.

     Here are the symbols:

     Number  Name  Command  Symbol

     1  asterisk  \ast  \ast,*

     2  dagger  \dagger

     3  ddagger  \ddagger

     4  section-sign  \S

     5  paragraph-sign  \P

     6  double-vert  \parallel

     7  double-asterisk  \ast\ast  \ast\ast,**

     8
     double-dagger  \dagger\dagger

     9
     double-ddagger  \ddagger\ddagger

\usecounter
===========

Synopsis:

     \usecounter{COUNTER}

Used in the second argument of the list environment (see list), this declares that list items will be numbered by COUNTER.  It initializes COUNTER to zero, and arranges that when \item is called without its optional argument then COUNTER is incremented by \refstepcounter, making its value be the current ref value (see \ref).  This command is fragile (see \protect).

Put in the document preamble, this example makes a new list environment enumerated with TESTCOUNTER:

     \newcounter{testcounter}
     \newenvironment{test}{%
       \begin{list}{}{%
         \usecounter{testcounter}
       }
     }{%
       \end{list}
     }

\value
======

Synopsis:

     \value{COUNTER}

Expands to the value of the counter COUNTER. (Note that the name of a counter does not begin with a backslash.)

This example outputs Test counter is 6. Other counter is 5..

     \newcounter{test} \setcounter{test}{5}
     \newcounter{other} \setcounter{other}{\value{test}}
     \addtocounter{test}{1}

     Test counter is \arabic{test}.
     Other counter is \arabic{other}.

The \value command is not used for typesetting the value of the counter.  For that, see \alph \Alph \arabic \roman \Roman \fnsymbol.

It is often used in \setcounter or \addtocounter but \value can be used anywhere that LaTeX expects a number, such as in \hspace{\value{foo}\parindent}.  It must not be preceded by \protect (see \protect).

This example inserts \hspace{4\parindent}.

     \setcounter{myctr}{3} \addtocounter{myctr}{1}
     \hspace{\value{myctr}\parindent}

\setcounter
===========

Synopsis:

     \setcounter{COUNTER}{VALUE}

Globally set the counter COUNTER to have the value of the VALUE argument, which must be an integer.  Thus, you can set a counter's value as \setcounter{section}{5}.  Note that the counter name does not start with a backslash.

In this example if the counter theorem has value 12 then the second line will print XII.

     \setcounter{exercise}{\value{theorem}}
     Here it is in Roman: \Roman{exercise}.

\addtocounter
=============

Synopsis:

     \addtocounter{COUNTER}{VALUE

Globally increment COUNTER by the amount specified by the VALUE argument, which may be negative.

In this example the section value appears as VII.

     \setcounter{section}{5}
     \addtocounter{section}{2}
     Here it is in Roman: \Roman{section}.

\refstepcounter
===============

Synopsis:

     \refstepcounter{COUNTER}

Globally increments the value of COUNTER by one, as does \stepcounter (see \stepcounter).  The difference is that this command resets the value of any counter numbered within it.  (For the definition of ``counters numbered within'', see \newcounter.)

In addition, this command also defines the current \ref value to be the result of \thecounter.

While the counter value is set globally, the \ref value is set locally, i.e., inside the current group.

\stepcounter
============

Synopsis:

     \stepcounter{COUNTER}

Globally adds one to COUNTER and resets all counters numbered within it.  (For the definition of ``counters numbered within'', see \newcounter.)

This command differs from \refstepcounter in that this one does not influence references --- it does not define the current \ref value to be the result of \thecounter (see \refstepcounter).

\day & \month & \year
=====================

LaTeX defines the counter \day for the day of the month (nominally with value between 1 and 31), \month for the month of the year (nominally with value between 1 and 12), and year \year. When TeX starts up, they are set from the current values on the system.  The related command \today produces a string representing the current day (see \today).

They counters are not updated as the job progresses so in principle they could be incorrect by the end.  In addition, TeX does no sanity check:

     \day=-2 \month=13 \year=-4 \today

gives no error or warning and results in the output -2, -4 (the bogus month value produces no output).

Lengths
*******

A length is a measure of distance.  Many LaTeX commands take a length as an argument.

Lengths come in two types.  A rigid length such as 10pt does not contain a plus or minus component.  (Plain TeX calls this a dimen.)  A rubber length (what Plain TeX calls a skip) such as as with 1cm plus0.05cm minus0.01cm can contain either or both of those components.  In that rubber length, the 1cm is the natural length while the other two, the plus and minus components, allow TeX to stretch or shrink the length to optimize placement.

The illustrations below use these two commands.

     % make a black bar 10pt tall and #1 wide
     \newcommand{\blackbar}[1]{\rule{#1}{10pt}}

     % Make a box around #2 that is #1 wide (excluding the border)
     \newcommand{\showhbox}[2]{%
       \fboxsep=0pt\fbox{\hbox to #1{#2}}}

This example uses those commands to show a black bar 100 points long between XXX and YYY.  This length is rigid.

     XXX\showhbox{100pt}{\blackbar{100pt}}YYY

As for rubber lengths, shrinking is simpler one: with 1cm minus 0.05cm, the natural length is 1cm but TeX can shrink it down as far as 0.95cm.  Beyond that, TeX refuses to shrink any more. Thus, below the first one works fine, producing a space of 98 points between the two bars.

     XXX\showhbox{300pt}{%
       \blackbar{101pt}\hspace{100pt minus 2pt}\blackbar{101pt}}YYY

     XXX\showhbox{300pt}{%
       \blackbar{105pt}\hspace{100pt minus 1pt}\blackbar{105pt}}YYY

But the second one gets a warning like Overfull \hbox (1.0pt too wide) detected at line 17.  In the output the first Y is overwritten by the end of the black bar, because the box's material is wider than the 300pt allocated, as TeX has refused to shrink the total to less than 309 points.

Stretching is like shrinking except that if TeX is asked to stretch beyond the given amount, it will do it.  Here the first line is fine, producing a space of 110 points between the bars.

     XXX\showhbox{300pt}{%
       \blackbar{95pt}\hspace{100pt plus 10pt}\blackbar{95pt}}YYY

     XXX\showhbox{300pt}{%
       \blackbar{95pt}\hspace{100pt plus 1pt}\blackbar{95pt}}YYY

In the second line TeX needs a stretch of 10 points and only 1 point was specified.  TeX stretches the space to the required length but it gives you a warning like Underfull \hbox (badness 10000) detected at line 22.  (We won't discuss badness.)

You can put both stretch and shrink in the same length, as in 1ex plus 0.05ex minus 0.02ex.

If TeX is setting two or more rubber lengths then it allocates the stretch or shrink in proportion.

     XXX\showhbox{300pt}{%
       \blackbar{100pt}%  left
       \hspace{0pt plus 50pt}\blackbar{80pt}\hspace{0pt plus 10pt}%  middle
       \blackbar{100pt}}YYY  % right

The left and right bars take up 100 points, so the middle needs another 100.  The middle bar is 80 points so the two \hspace's must stretch 20 points.  Because the two are plus 50pt and plus 10pt, TeX gets 5/6 of the stretch from the first space and 1/6 from the second.

The plus or minus component of a rubber length can contain a fill component, as in 1in plus2fill.  This gives the length infinite stretchability or shrinkability so that TeX could set it to any distance.  Here the two figures will be equal-spaced across the page.

     \begin{minipage}{\linewidth}
       \hspace{0pt plus 1fill}\includegraphics{godel.png}%
       \hspace{0pt plus 1fill}\includegraphics{einstein.png}%
       \hspace{0pt plus 1fill}
     \end{minipage}

TeX actually has three levels of infinity for glue components: fil, fill, and filll.  The later ones are more infinite than the earlier ones.  Ordinarily document authors only use the middle one (see \hfill and see \vfill).

Multiplying a rubber length by a number turns it into a rigid length, so that after \setlength{\ylength}{1in plus 0.2in} and \setlength{\zlength}{3\ylength} then the value of \zlength is 3in.

Units of length
===============

TeX and LaTeX know about these units both inside and outside of math mode.

pt
     Point, 1/72.27 inch.  The conversion to metric units, to two decimal places, is 1point = 2.85mm = 28.45cm.

pc
     Pica, 12 pt

in
     Inch,  72.27 pt

bp
     Big point, 1/72 inch.  This length is the definition of a point in PostScript and many desktop publishing systems.

cm
     Centimeter

mm
     Millimeter

dd
     Didot point, 1.07 pt

cc
     Cicero, 12 dd

sp
     Scaled point, 1/65536 pt

Two other lengths that are often used are values set by the designer of the font.  The x-height of the current font ex, traditionally the height of the lowercase letter x, is often used for vertical lengths. Similarly em, traditionally the width of the capital letter M, is often used for horizontal lengths (there is also \enspace, which is 0.5em).  Use of these can help make a definition work better across font changes.  For example, a definition of the vertical space between list items given as \setlength{\itemsep}{1ex plus 0.05ex minus 0.01ex} is more likely to still be reasonable if the font is changed than a definition given in points.

In math mode, many definitions are expressed in terms of the math unit mu given by 1 em = 18 mu, where the em is taken from the current math symbols family.  See Spacing in math mode.

\setlength
==========

Synopsis:

     \setlength{LEN}{AMOUNT}

Set the length LEN to AMOUNT.  The length name LEN must begin with a backslash, \.  The amount can be a rubber length (see Lengths).  It can be positive, negative or zero, and can be in any units that LaTeX understands (see Units of length).

Below, with LaTeX's defaults the first paragraph will be indented while the second will not.

     I told the doctor I broke my leg in two places.

     \setlength{\parindent}{0em}
     He said stop going to those places.

If you did not declare LEN with \newlength, for example if you mistype the above as \newlength{\specparindent}\setlength{\sepcparindent}{...}, then you get an error like Undefined control sequence. <argument> \sepcindent.  If you omit the backslash at the start of the length name then you get an error like Missing number, treated as zero. <to be read again> \relax l.19 \setlength{specparindent}{0.6\parindent}

\addtolength
============

Synopsis:

     \addtolength{LEN}{AMOUNT}

Increment the length LEN by AMOUNT.  The length name LEN begins with a backslash, \.  The amount is a rubber length (see Lengths).  It can be positive, negative or zero, and can be in any units that LaTeX understands (see Units of length).

Below, if \parskip starts with the value 0pt plus 1pt

     Doctor: how is the boy who swallowed the silver dollar?
     \addtolength{\parskip}{1pt}

     Nurse: no change.

then it has the value 1pt plus 1pt for the second paragraph.

If you did not declare the length LEN with \newlength, if for example you mistype the above as \addtolength{\specparindent}{0.6\praindent}, then you get something like Undefined control sequence. <argument> \praindent. If you leave off the backslash at the start of LEN, as in \addtolength{parindent}{1pt}, then you get something like You can't use `the letter p' after \advance.

\settodepth
===========

Synopsis:

     \settodepth{LEN}{TEXT}

Set the length LEN to the depth of box that LaTeX gets on typesetting the TEXT argument.  The length name LEN must begin with a backslash, \.

This will show how low the character descenders go.

     \newlength{\alphabetdepth}
     \settodepth{\alphabetdepth}{abcdefghijklmnopqrstuvwxyz}
     \the\alphabetdepth

If you did not set aside the length LEN, if for example you mistype the above as \settodepth{\aplhabetdepth}{abc...}, then you get something like Undefined control sequence. <argument> \aplhabetdepth.  If you leave the backslash out of LEN, as in \settodepth{alphabetdepth}{...} then you get something like Missing number, treated as zero. <to be read again> \setbox.

\settoheight
============

Synopsis:

     \settoheight{LEN}{text}

Sets the length LEN to the height of box that LaTeX gets on typesetting the text argument.  The length name LEN must begin with a backslash, \.

This will show how high the characters go.

     \newlength{\alphabetheight}
     \settoheight{\alphabetheight}{abcdefghijklmnopqrstuvwxyz}
     \the\alphabetheight

If no such length LEN has been declared with \newlength, if for example you mistype as \settoheight{\aplhabetheight}{abc...}, then you get something like Undefined control sequence. <argument> \alphabetheight.  If you leave the backslash out of LEN, as in \settoheight{alphabetheight}{...} then you get something like Missing number, treated as zero. <to be read again> \setbox.

\settowidth
===========

Synopsis:

     \settowidth{LEN}{TEXT}

Set the length LEN to the width of the box that LaTeX gets on typesetting the TEXT argument.  The length name LEN must begin with a backslash, \.

This measures the width of the lowercase ASCII alphabet.

     \newlength{\alphabetwidth}
     \settowidth{\alphabetwidth}{abcdefghijklmnopqrstuvwxyz}
     \the\alphabetwidth

If no such length LEN has been set aside, if for example you mistype the above as \settowidth{\aplhabetwidth}{abc...}, then you get something like Undefined control sequence. <argument> \aplhabetwidth.  If you leave the backslash out of LEN, as in \settoheight{alphabetwidth}{...} then you get something like Missing number, treated as zero. <to be read again> \setbox.

Making paragraphs
*****************

To start a paragraph, just type some text.  To end the current paragraph, put an empty line.  This is three paragraphs, separated by two empty lines.

     It is a truth universally acknowledged, that a single man in possession
     of a good fortune, must be in want of a wife.

     However little known the feelings or views of such a man may be on his
     first entering a neighbourhood, this truth is so well fixed in the minds
     of the surrounding families, that he is considered the rightful property
     of some one or other of their daughters.

     ``My dear Mr. Bennet,'' said his lady to him one day,
     ``have you heard that Netherfield Park is let at last?''

The separator lines must be empty, including not containing a comment character, %.

Once LaTeX has gathered all of a paragraph's contents it divides that content into lines in a way that is optimized over the entire paragraph (see Line breaking).

There are places where a new paragraph is not permitted.  Don't put a blank line in math mode (see Modes); here the line before the \end{equation}

     \begin{equation}
       2^{|S|} > |S|

     \end{equation}

will get you the error Missing $ inserted.  Similarly, the blank line in this section argument

     \section{aaa

     bbb}

gets Runaway argument? {aaa ! Paragraph ended before \@sect was complete.

\par
====

Synopsis (note that while reading the input TeX converts two consecutive newlines to a \par):

     \par

End the current paragraph.  The usual way to separate paragraphs is with a blank line but the \par command is entirely equivalent.  This command is robust (see \protect).

This example uses \par rather than a blank line simply for readability.

     \newcommand{\syllabusLegalese}{%
       \whatCheatingIs\par\whatHappensWhenICatchYou}

In LR mode or a vertical mode the \par command does nothing but it terminates paragraph mode, switching LaTeX to vertical mode (see Modes).

You cannot use the \par command in a math mode.  You also cannot use it in the argument of many commands, such as the \section command (see Making paragraphs and \newcommand & \renewcommand).

The \par command is not the same as the \paragraph command. The latter is, like \section or \subsection, a sectioning unit used by the standard LaTeX documents (see \subsubsection & \paragraph & \subparagraph).

The \par command is not the same as \newline or the line break double backslash, \\.  The difference is that \par ends the paragraph, not just the line, and also triggers the addition of the between-paragraph vertical space \parskip (see \parindent & \parskip).

The output from this example

     xyz

     \setlength{\parindent}{3in}
     \setlength{\parskip}{5in}
     \noindent test\indent test1\par test2

is: after xyz there is a vertical skip of 5 inches and then test appears, aligned with the left margin.  On the same line, there is an empty horizontal space of 3 inches and then test1 appears.  Finally. there is a vertical space of 5 inches, followed by a fresh paragraph with a paragraph indent of 3 inches, and then LaTeX puts the text test2.

\indent & \noindent
===================

Synopsis:

     \indent

or

     \noindent

Go into horizontal mode (see Modes).  The \indent command first outputs an empty box whose width is \parindent.  These commands are robust (see \protect).

Ordinarily you create a new paragraph by putting in a blank line. See \par for the difference between this command and \par.  To start a paragraph without an indent, or to continue an interrupted paragraph, use \noindent.

In the middle of a paragraph the \noindent command has no effect, because LaTeX is already in horizontal mode there.  The \indent command's only effect is to output a space.

This example starts a fresh paragraph.

     ... end of the prior paragraph.

     \noindent This paragraph is not indented.

and this continues an interrupted paragraph.

     The data

     \begin{center}
       \begin{tabular}{rl} ... \end{tabular}
     \end{center}

     \noindent shows this clearly.

To omit indentation in the entire document put \setlength{\parindent}{0pt} in the preamble.  If you do that, you may want to also set the length of spaces between paragraphs, \parskip (see \parindent & \parskip).

Default LaTeX styles have the first paragraph after a section that is not indented, as is traditional typesetting in English.  To change that, look on CTAN for the package indentfirst.

\parindent & \parskip
=====================

Synopsis:

     \setlength{\parskip}{HORIZONTAL LEN}
     \setlength{\parinden}{VERTICAL LEN}

Both are a rubber lengths (see Lengths).  They give the indentation of ordinary paragraphs, not paragraphs inside minipages (see minipage), and the vertical space between paragraphs.

This, put in the preamble,

     \setlength{\parindent}{0em}
     \setlength{\parskip}{1ex}

arranges that the document will have paragraphs that are not indented, but instead are vertically separated by about the height of a lowercase x.

In standard LaTeX documents, the default value for \parindent in one-column documents is 15pt when the default text size is 10pt , 17pt for 11pt, and 1.5em for 12pt.  In two-column documents it is 1em.  The default value for \parskip in LaTeX's standard document styles is 0pt plus1pt.

Marginal notes
==============

Synopsis, one of:

     \marginpar{RIGHT}
     \marginpar[LEFT]{RIGHT}

Create a note in the margin.  The first line of the note will have the same baseline as the line in the text where the \marginpar occurs.

The margin that LaTeX uses for the note depends on the current layout (see Document class options) and also on \reversemarginpar (see below).  If you are using one-sided layout (document option oneside) then it goes in the right margin.  If you are using two-sided layout (document option twoside) then it goes in the outside margin.  If you are in two-column layout (document option twocolumn) then it goes in the nearest margin.

If you declare \reversemarginpar then LaTeX will place subsequent marginal notes in the opposite margin to that given in the prior paragraph.  Revert that to the default position with \normalmarginpar.

When you specify the optional argument LEFT then it is used for a note in the left margin, while the mandatory argument RIGHT is used for a note in the right margin.

Normally, a note's first word will not be hyphenated.  You can enable hyphenation there by beginning LEFT or RIGHT with \hspace{0pt}.

These parameters affect the formatting of the note:

\marginparpush
     Minimum vertical space between notes; default 7pt for 12pt documents, 5pt else.

\marginparsep
     Horizontal space between the main text and the note; default 11pt for 10pt documents, 10pt else.

\marginparwidth
     Width of the note itself; default for a one-sided 10pt document is 90pt, 83pt for 11pt, and 68pt for 12pt; 17pt more in each case for a two-sided document. In two column mode, the default is 48pt.

The standard LaTeX routine for marginal notes does not prevent notes from falling off the bottom of the page.

Math formulas
*************

Produce mathematical text by putting LaTeX into math mode or display math mode (see Modes).  This example shows both.

     The wave equation for \( u \) is
     \begin{displaymath}
       \frac{\partial^2u}{\partial t^2} = c^2\nabla^2u
     \end{displaymath}
     where \( \nabla^2 \) is the spatial Laplacian and \( c \) is constant.

Math mode is for inline mathematics.  In the above example it is invoked by the starting \( and finished by the matching ending \). Display math mode is for displayed equations and here is invoked by the displaymath environment.  Note that any mathematical text whatever, including mathematical text consisting of just one character, is handled in math mode.

When in math mode or display math mode, LaTeX handles many aspects of your input text differently than in other text modes.  For example,

     contrast x+y with \( x+y \)

in math mode the letters are in italics and the spacing around the plus sign is different.

There are three ways to make inline formulas, to put LaTeX in math mode.

     \( MATHEMATICAL MATERIAL \)
     $ MATHEMATICAL MATERIAL $
     \begin{math} MATHEMATICAL MATERIAL \end{math}

The first form is preferred and the second is quite common, but the third form is rarely used.  You can sometimes use one and sometimes another, as in \(x\) and $y$.  You can use these in paragraph mode or in LR mode (see Modes).

To make displayed formulas, put LaTeX into display math mode with either:

     \begin{displaymath}
       MATHEMATICAL MATERIAL
     \end{displaymath}

or

     \begin{equation}
       MATHEMATICAL MATERIAL
     \end{equation}

(see displaymath, see equation).  The only difference is that with the equation environment, LaTeX puts a formula number alongside the formula.  The construct \[ MATH \] is equivalent to \begin{displaymath} MATH \end{displaymath}.  These environments can only be used in paragraph mode (see Modes).

The two mathematics modes are similar, but there are some differences. One involves the placement of subscripts and superscripts; in display math mode they are further apart and in inline math mode they are closer together.

Sometimes you want the display math typographical treatment to happen in the inline math mode.  For this, the \displaystyle declaration forces the size and style of the formula to be that of displaymath.  Thus \(\displaystyle \sum_{n=0}^\infty x_n\) will have the limits above and below the summation sign, not next to it.  Another example is that

     \begin{tabular}{r|cc}
       \textsc{Name}  &\textsc{Series}  &\textsc{Sum}  \\  \hline
       Arithmetic     &\( a+(a+b)+(a+2b)+\cdots+(a+(n-1)b) \)
                        &\( na+(n-1)n\cdot\frac{b}{2}\)  \\
       Geometric      &\( a+ab+ab^2+\cdots+ab^{n-1} \)
                        &\(\displaystyle a\cdot\frac{1-b^n}{1-b}\)  \\
     \end{tabular}

because it has no \displaystyle, the Arithmetic line's fraction will be scrunched.  But, because of its \displaystyle, the Geometric line's fraction will be easy to read, with characters the same size as in the rest of the line.

The American Mathematical Society has made freely available a set of packages that greatly expand your options for writing mathematics, amsmath and amssymb (also be aware of the mathtools package that is an extension to, and loads, amsmath).  New documents that will have mathematical text should use these packages. Descriptions of these packages is outside the scope of this document; see their documentation on CTAN.

Subscripts & superscripts
=========================

Synopsis (in math mode or display math mode), one of:

     BASE^EXP
     BASE^{EXP}

or, one of:

     BASE_EXP
     BASE_{EXP}

Make EXP appear as a superscript of BASE (with the caret character, ^) or a subscript (with underscore, _).

In this example the 0's and 1's are subscripts while the 2's are superscripts.

     \( (x_0+x_1)^2 \leq (x_0)^2+(x_1)^2 \)

To have the subscript or superscript contain more than one character, surround the expression with curly braces, as in e^{-2x}. This example's fourth line shows curly braces used to group an expression for the exponent.

     \begin{displaymath}
       (3^3)^3=27^3=19\,683
       \qquad
       3^{(3^3)}=3^{27}=7\,625\,597\,484\,987
     \end{displaymath}

LaTeX knows how to handle a superscript on a superscript, or a subscript on a subscript, or supers on subs, or subs on supers.  So, expressions such as e^{x^2} and x_{i_0} give correct output.  Note the use in those expressions of curly braces to give the BASE a determined EXP.  If you enter \(3^3^3\) then you get Double superscript.

LaTeX does the right thing when something has both a subscript and a superscript.  In this example the integral has both.  They come out in the correct place without any author intervention.

     \begin{displaymath}
       \int_{x=a}^b f'(x)\,dx = f(b)-f(a)
     \end{displaymath}

Note the parentheses around x=a to make the entire expression a subscript.

To put a superscript or subscript before a symbol, use a construct like {}_t K^2.  The empty curly braces {} give the subscript something to attach to and keeps it from accidentally attaching to a prior symbols.

Using the subscript or superscript command outside of math mode or display math mode, as in the expression x^2, will get you the error Missing $ inserted.

A common reason to want subscripts outside of a mathematics mode is to typeset chemical formulas.  There are packages for that such as mhchem; see CTAN.

Math symbols
============

LaTeX provides almost any mathematical or technical symbol that anyone uses.  For example, if you include $\pi$ in your source, you will get the pi symbol.  See the Comprehensive
LaTeX Symbol List at https://ctan.org/tex-archive/info/symbols/comprehensive/.

Here is a list of commonly-used symbols.  It is by no means exhaustive. Each symbol is described with a short phrase, and its symbol class, which determines the spacing around it, is given in parenthesis.  Unless said otherwise, the commands for these symbols can be used only in math mode.  To redefine a command so that it can be used whatever the current mode, see \ensuremath.

\|
     Parallel (relation). Synonym: \parallel.

\aleph
     Aleph, transfinite cardinal (ordinary).

\alpha
     Lowercase Greek letter alpha (ordinary).

\amalg
     Disjoint union (binary)

\angle
     Geometric angle (ordinary). Similar: less-than sign < and angle bracket \langle.

\approx
     Almost equal to (relation).

\ast
     Asterisk operator, convolution, six-pointed (binary). Synonym: *, which is often a superscript or subscript, as in the Kleene star. Similar: \star, which is five-pointed, and is sometimes used as a general binary operation, and sometimes reserved for cross-correlation.

\asymp
     Asymptotically equivalent (relation).

\backslash
     \ Backslash (ordinary).  Similar: set minus \setminus, and \textbackslash for backslash outside of math mode.

\beta
     Lowercase Greek letter beta (ordinary).

\bigcap
     Variable-sized, or n-ary, intersection (operator). Similar: binary intersection \cap.

\bigcirc
     Circle, larger (binary).  Similar: function composition \circ.

\bigcup
     Variable-sized, or n-ary, union (operator). Similar: binary union \cup.

\bigodot
     Variable-sized, or n-ary, circled dot operator (operator).

\bigoplus
     Variable-sized, or n-ary, circled plus operator (operator).

\bigotimes
     Variable-sized, or n-ary, circled times operator (operator).

\bigtriangledown
     Variable-sized, or n-ary, open triangle pointing down (operator).

\bigtriangleup
     Variable-sized, or n-ary, open triangle pointing up (operator).

\bigsqcup
     Variable-sized, or n-ary, square union (operator).

\biguplus
     Variable-sized, or n-ary, union operator with a plus (operator).  (Note that the name has only one p.)

\bigvee
     Variable-sized, or n-ary, logical-and (operator).

\bigwedge
     Variable-sized, or n-ary, logical-or (operator).

\bot
     Up tack, bottom, least element of a partially ordered set, or a contradiction (ordinary).  See also \top.

\bowtie
     Natural join of two relations (relation).

\Box
     Modal operator for necessity; square open box (ordinary).  Not available in plain TeX. In LaTeX you need to load the amssymb package.

\bullet
     Bullet (binary).  Similar: multiplication dot \cdot.

\cap
     Intersection of two sets (binary).  Similar: variable-sized operator \bigcap.

\cdot
     Multiplication (binary).  Similar: Bullet dot \bullet.

\chi
     Lowercase Greek chi (ordinary).

\circ
     Function composition, ring operator (binary).  Similar: variable-sized operator \bigcirc.

\clubsuit
     Club card suit (ordinary).

\complement
     Set complement, used as a superscript as in $S^\complement$ (ordinary).  Not available in plain TeX. In LaTeX you need to load the amssymb package. Also used: $S^{\mathsf{c}}$ or $\bar{S}$.

\cong
     Congruent (relation).

\coprod
     Coproduct (operator).

\cup
     Union of two sets (binary).  Similar: variable-sized operator \bigcup.

\dagger
     Dagger relation (binary).

\dashv
     Dash with vertical, reversed turnstile (relation).  Similar: turnstile \vdash.

\ddagger
     Double dagger relation (binary).

\Delta
     Greek uppercase delta, used for increment (ordinary).

\delta
     Greek lowercase delta (ordinary).

\Diamond
     Large diamond operator (ordinary).  Not available in plain TeX. In LaTeX you need to load the amssymb package.

\diamond
     Diamond operator (binary).  Similar: large diamond \Diamond, circle bullet \bullet.

\diamondsuit
     Diamond card suit (ordinary).

\div
     Division sign (binary).

\doteq
     Approaches the limit (relation).  Similar: geometrically equal to \Doteq.

\downarrow
     Down arrow, converges (relation).  Similar: \Downarrow double line down arrow.

\Downarrow
     Double line down arrow (relation).  Similar: \downarrow single line down arrow.

\ell
     Lowercase cursive letter l (ordinary).

\emptyset
     Empty set symbol (ordinary).  The variant form is \varnothing.

\epsilon
     Lowercase lunate epsilon (ordinary). Similar to Greek text letter. More widely used in mathematics is the script small letter epsilon \varepsilon. Related: the set membership relation \in.

\equiv
     Equivalence (relation).

\eta
     Lowercase Greek letter (ordinary).

\exists
     Existential quantifier (ordinary).

\flat
     Musical flat (ordinary).

\forall
     Universal quantifier (ordinary).

\frown
     Downward curving arc (ordinary).

\Gamma
     uppercase Greek letter (ordinary).

\gamma
     Lowercase Greek letter (ordinary).

\ge
     Greater than or equal to (relation).  This is a synonym for \geq.

\geq
     Greater than or equal to (relation).  This is a synonym for \ge.

\gets
     Is assigned the value (relation). Synonym: \leftarrow.

\gg
     Much greater than (relation).  Similar: much less than \ll.

\hbar
     Planck constant over two pi (ordinary).

\heartsuit
     Heart card suit (ordinary).

\hookleftarrow
     Hooked left arrow (relation).

\hookrightarrow
     Hooked right arrow (relation).

\iff
     If and only if (relation).  It is \Longleftrightarrow with a \thickmuskip on either side.

\Im
     Imaginary part (ordinary).  See: real part \Re.

\imath
     Dotless i; used when you are putting an accent on an i (see Math accents).

\in
     Set element (relation).  See also: lowercase lunate epsilon \epsilon and small letter script epsilon \varepsilon.

\infty
     Infinity (ordinary).

\int
     Integral (operator).

\iota
     Lowercase Greek letter (ordinary).

\Join
     Condensed bowtie symbol (relation).  Not available in Plain TeX.

\jmath
     Dotless j; used when you are putting an accent on a j (see Math accents).

\kappa
     Lowercase Greek letter (ordinary).

\Lambda
     uppercase Greek letter (ordinary).

\lambda
     Lowercase Greek letter (ordinary).

\land
     Logical and (binary).  This is a synonym for \wedge. See also logical or \lor.

\langle
     Left angle, or sequence, bracket (opening).  Similar: less-than <. Matches \rangle.

\lbrace
     Left curly brace (opening). Synonym: \{. Matches \rbrace.

\lbrack
     Left square bracket (opening). Synonym: [. Matches \rbrack.

\lceil
     Left ceiling bracket, like a square bracket but with the bottom shaved off (opening). Matches \rceil.

\le
     Less than or equal to (relation).  This is a synonym for \leq.

\leadsto
     Squiggly right arrow (relation).  Not available in plain TeX. In LaTeX you need to load the amssymb package. To get this symbol outside of math mode you can put \newcommand*{\Leadsto}{\ensuremath{\leadsto}} in the preamble and then use \Leadsto instead.

\Leftarrow
     Is implied by, double-line left arrow (relation).  Similar: single-line left arrow \leftarrow.

\leftarrow
     Single-line left arrow (relation). Synonym: \gets. Similar: double-line left arrow \Leftarrow.

\leftharpoondown
     Single-line left harpoon, barb under bar (relation).

\leftharpoonup
     Single-line left harpoon, barb over bar (relation).

\Leftrightarrow
     Bi-implication; double-line double-headed arrow (relation). Similar: single-line double headed arrow \leftrightarrow.

\leftrightarrow
     Single-line double-headed arrow (relation).  Similar: double-line double headed arrow \Leftrightarrow.

\leq
     Less than or equal to (relation).  This is a synonym for \le.

\lfloor
     Left floor bracket (opening). Matches: \floor.

\lhd
     Arrowhead, that is, triangle, pointing left (binary). Not available in plain TeX. In LaTeX you need to load the amssymb package. For the normal subgroup symbol you should load amssymb and use \vartriangleleft (which is a relation and so gives better spacing).

\ll
     Much less than (relation).  Similar: much greater than \gg.

\lnot
     Logical negation (ordinary). Synonym: \neg.

\longleftarrow
     Long single-line left arrow (relation).  Similar: long double-line left arrow \Longleftarrow.

\longleftrightarrow
     Long single-line double-headed arrow (relation).  Similar: long double-line double-headed arrow \Longleftrightarrow.

\longmapsto
     Long single-line left arrow starting with vertical bar (relation).  Similar: shorter version \mapsto.

\longrightarrow
     Long single-line right arrow (relation).  Similar: long double-line right arrow \Longrightarrow.

\lor
     Logical or (binary).  Synonym: wedge \wedge.

\mapsto
     Single-line left arrow starting with vertical bar (relation). Similar: longer version \longmapsto.

\mho
     Conductance, half-circle rotated capital omega (ordinary). Not available in plain TeX. In LaTeX you need to load the amssymb package.

\mid
     Single-line vertical bar (relation).  A typical use of \mid is for a set \{\, x \mid x\geq 5 \,\}.

     Similar: \vert and | produce the same single-line vertical bar symbol but without any spacing (they fall in class ordinary) and you should not use them as relations but instead only as ordinals, i.e., footnote symbols.  For absolute value, see the entry for \vert and for norm see the entry for \Vert.

\models
     Entails, or satisfies; double turnstile, short double dash (relation).  Similar: long double dash \vDash.

\mp
     Minus or plus (relation).

\mu
     Lowercase Greek letter (ordinary).

\nabla
     Hamilton's del, or differential, operator (ordinary).

\natural
     Musical natural notation (ordinary).

\ne
     Not equal (relation). Synonym: \neq.

\nearrow
     North-east arrow (relation).

\neg
     Logical negation (ordinary). Synonym: \lnot. Sometimes instead used for negation: \sim.

\neq
     Not equal (relation). Synonym: \ne.

\ni
     Reflected membership epsilon; has the member (relation). Synonym: \owns. Similar: is a member of \in.

\not
     Long solidus, or slash, used to overstrike a following operator (relation).

     Many negated operators are available that don't require \not, particularly with the amssymb package. For example, \notin is typographically preferable to \not\in.

\notin
     Not an element of (relation).  Similar: not subset of \nsubseteq.

\nu
     Lowercase Greek letter (ordinary).

\nwarrow
     North-west arrow (relation).

\odot
     Dot inside a circle (binary).  Similar: variable-sized operator \bigodot.

\oint
     Contour integral, integral with circle in the middle (operator).

\Omega
     uppercase Greek letter (ordinary).

\omega
     Lowercase Greek letter (ordinary).

\ominus
     Minus sign, or dash, inside a circle (binary).

\oplus
     Plus sign inside a circle (binary).  Similar: variable-sized operator \bigoplus.

\oslash
     Solidus, or slash, inside a circle (binary).

\otimes
     Times sign, or cross, inside a circle (binary).  Similar: variable-sized operator \bigotimes.

\owns
     Reflected membership epsilon; has the member (relation). Synonym: \ni. Similar: is a member of \in.

\parallel
     Parallel (relation). Synonym: \|.

\partial
     Partial differential (ordinary).

\perp
     Perpendicular (relation).  Similar: \bot uses the same glyph but the spacing is different because it is in the class ordinary.

\phi
     Lowercase Greek letter (ordinary).  The variant form is \varphi.

\Pi
     uppercase Greek letter (ordinary).

\pi
     Lowercase Greek letter (ordinary).  The variant form is \varpi.

\pm
     Plus or minus (binary).

\prec
     Precedes (relation). Similar: less than <.

\preceq
     Precedes or equals (relation). Similar: less than or equals \leq.

\prime
     Prime, or minute in a time expression (ordinary). Typically used as a superscript: $f^\prime$; $f^\prime$ and $f'$ produce the same result.  An advantage of the second is that $f'''$ produces the desired symbol, that is, the same result as $f^{\prime\prime\prime}$, but uses rather less typing.  You can only use \prime in math mode.  Using the right single quote ' in text mode produces a different character (apostrophe).

\prod
     Product (operator).

\propto
     Is proportional to (relation)

\Psi
     uppercase Greek letter (ordinary).

\psi
     Lowercase Greek letter (ordinary).

\rangle
     Right angle, or sequence, bracket (closing). Similar: greater than >. Matches:\langle.

\rbrace
     Right curly brace (closing). Synonym: \}. Matches \lbrace.

\rbrack
     Right square bracket (closing). Synonym: ]. Matches \lbrack.

\rceil
     Right ceiling bracket (closing). Matches \lceil.

\Re
     Real part, real numbers, cursive capital R (ordinary). Related: double-line, or blackboard bold, R \mathbb{R}; to access this, load the amsfonts package.

\restriction
     Restriction of a function (relation). Synonym: \upharpoonright.  Not available in plain TeX. In LaTeX you need to load the amssymb package.

\revemptyset
     Reversed empty set symbol (ordinary).  Related: \varnothing. Not available in plain TeX. In LaTeX you need to load the stix package.

\rfloor
     Right floor bracket, a right square bracket with the top cut off (closing). Matches \lfloor.

\rhd
     Arrowhead, that is, triangle, pointing right (binary). Not available in plain TeX. In LaTeX you need to load the amssymb package. For the normal subgroup symbol you should instead load amssymb and use \vartriangleright (which is a relation and so gives better spacing).

\rho
     Lowercase Greek letter (ordinary).  The variant form is \varrho.

\Rightarrow
     Implies, right-pointing double line arrow (relation). Similar: right single-line arrow \rightarrow.

\rightarrow
     Right-pointing single line arrow (relation). Synonym: \to. Similar: right double line arrow \Rightarrow.

\rightharpoondown
     Right-pointing harpoon with barb below the line (relation).

\rightharpoonup
     Right-pointing harpoon with barb above the line (relation).

\rightleftharpoons
     Right harpoon up above left harpoon down (relation).

\searrow
     Arrow pointing southeast (relation).

\setminus
     Set difference, reverse solidus or reverse slash, like \ (binary). Similar: backslash \backslash and also \textbackslash outside of math mode.

\sharp
     Musical sharp (ordinary).

\Sigma
     uppercase Greek letter (ordinary).

\sigma
     Lowercase Greek letter (ordinary). The variant form is \varsigma.

\sim
     Similar, in a relation (relation).

\simeq
     Similar or equal to, in a relation (relation).

\smallint
     Integral sign that does not change to a larger size in a display (operator).

\smile
     Upward curving arc, smile (ordinary).

\spadesuit
     Spade card suit (ordinary).

\sqcap
     Square intersection symbol (binary). Similar: intersection cap.

\sqcup
     Square union symbol (binary). Similar: union cup. Related: variable-sized operator \bigsqcup.

\sqsubset
     Square subset symbol (relation). Similar: subset \subset. Not available in plain TeX. In LaTeX you need to load the amssymb package.

\sqsubseteq
     Square subset or equal symbol (binary). Similar: subset or equal to \subseteq.

\sqsupset
     Square superset symbol (relation). Similar: superset \supset. Not available in plain TeX. In LaTeX you need to load the amssymb package.

\sqsupseteq
     Square superset or equal symbol (binary). Similar: superset or equal \supseteq.

\star
     Five-pointed star, sometimes used as a general binary operation but sometimes reserved for cross-correlation (binary). Similar: the synonyms asterisk * and \ast, which are six-pointed, and more often appear as a superscript or subscript, as with the Kleene star.

\subset
     Subset (occasionally, is implied by) (relation).

\subseteq
     Subset or equal to (relation).

\succ
     Comes after, succeeds (relation). Similar: is less than >.

\succeq
     Succeeds or is equal to (relation). Similar: less than or equal to \leq.

\sum
     Summation (operator). Similar: Greek capital sigma \Sigma.

\supset
     Superset (relation).

\supseteq
     Superset or equal to (relation).

\surd
     Radical symbol (ordinary).  The LaTeX command \sqrt{...} typesets the square root of the argument, with a bar that extends to cover the argument.

\swarrow
     Southwest-pointing  arrow (relation).

\tau
     Lowercase Greek letter (ordinary).

\theta
     Lowercase Greek letter (ordinary). The variant form is \vartheta.

\times
     Primary school multiplication sign (binary). See also \cdot.

\to
     Right-pointing single line arrow (relation). Synonym: \rightarrow.

\top
     Top, greatest element of a partially ordered set (ordinary). See also \bot.

\triangle
     Triangle (ordinary).

\triangleleft
     Not-filled triangle pointing left (binary). Similar: \lhd. For the normal subgroup symbol you should load amssymb and use \vartriangleleft (which is a relation and so gives better spacing).

\triangleright
     Not-filled triangle pointing right (binary). For the normal subgroup symbol you should instead load amssymb and use \vartriangleright (which is a relation and so gives better spacing).

\unlhd
     Left-pointing not-filled underlined arrowhead, that is, triangle, with a line under (binary). Not available in plain TeX. In LaTeX you need to load the amssymb package. For the normal subgroup symbol load amssymb and use \vartrianglelefteq (which is a relation and so gives better spacing).

\unrhd
     Right-pointing not-filled underlined arrowhead, that is, triangle, with a line under (binary). Not available in plain TeX. In LaTeX you need to load the amssymb package. For the normal subgroup symbol load amssymb and use \vartrianglerighteq (which is a relation and so gives better spacing).

\Uparrow
     Double-line upward-pointing arrow (relation). Similar: single-line up-pointing arrow \uparrow.

\uparrow
     Single-line upward-pointing arrow, diverges (relation). Similar: double-line up-pointing arrow \Uparrow.

\Updownarrow
     Double-line upward-and-downward-pointing arrow (relation). Similar: single-line upward-and-downward-pointing arrow \updownarrow.

\updownarrow
     Single-line upward-and-downward-pointing arrow (relation). Similar: double-line upward-and-downward-pointing arrow \Updownarrow.

\upharpoonright
     Up harpoon, with barb on right side (relation). Synonym: \restriction. Not available in plain TeX. In LaTeX you need to load the amssymb package.

\uplus
     Multiset union, a union symbol with a plus symbol in the middle (binary). Similar: union \cup. Related: variable-sized operator \biguplus.

\Upsilon
     uppercase Greek letter (ordinary).

\upsilon
     Lowercase Greek letter (ordinary).

\varepsilon
     Small letter script epsilon (ordinary).  This is more widely used in mathematics than the non-variant lunate epsilon form \epsilon. Related: set membership \in.

\vanothing
     Empty set symbol. Similar: \emptyset. Related: \revemptyset. Not available in plain TeX. In LaTeX you need to load the amssymb package.

\varphi
     Variant on the lowercase Greek letter (ordinary). The non-variant form is \phi.

\varpi
     Variant on the lowercase Greek letter (ordinary). The non-variant form is \pi.

\varrho
     Variant on the lowercase Greek letter (ordinary). The non-variant form is \rho.

\varsigma
     Variant on the lowercase Greek letter (ordinary).  The non-variant form is \sigma.

\vartheta
     Variant on the lowercase Greek letter (ordinary).  The non-variant form is \theta.

\vdash
     Provable; turnstile, vertical and a dash (relation). Similar: turnstile rotated a half-circle \dashv.

\vee
     Logical or; a downwards v shape (binary). Related: logical and \wedge. Similar: variable-sized operator \bigvee.

\Vert
     Vertical double bar (ordinary). Similar: vertical single bar \vert.

     For a norm symbol, you can use the mathtools package and put in your preamble \DeclarePairedDelimiter\norm{\lVert}{\rVert}. This gives you three command variants for double-line vertical bars that are correctly horizontally spaced: if in the document body you write the starred version $\norm*{M^\perp}$ then the height of the vertical bars will match the height of the argument, whereas with \norm{M^\perp} the bars do not grow with the height of the argument but instead are the default height, and \norm[SIZE COMMAND]{M^\perp} also gives bars that do not grow but are set to the size given in the SIZE COMMAND, e.g., \Bigg.

\vert
     Single line vertical bar (ordinary). Similar: double-line vertical bar \Vert. For such that, as in the definition of a set, use \mid because it is a relation.

     For absolute value you can use the mathtools package and in your preamble put \DeclarePairedDelimiter\abs{\lvert}{\rvert}. This gives you three command variants for single-line vertical bars that are correctly horizontally spaced: if in the document body you write the starred version $\abs*{\frac{22}{7}}$ then the height of the vertical bars will match the height of the argument, whereas with \abs{\frac{22}{7}} the bars do not grow with the height of the argument but instead are the default height, and \abs[SIZE COMMAND]{\frac{22}{7}} also gives bars that do not grow but are set to the size given in the SIZE COMMAND, e.g., \Bigg.

\wedge
     Logical and (binary).  Synonym: \land.  See also logical or \vee. Similar: variable-sized operator \bigwedge.

\wp
     Weierstrass p (ordinary).

\wr
     Wreath product (binary).

\Xi
     uppercase Greek letter (ordinary).

\xi
     Lowercase Greek letter (ordinary).

\zeta
     Lowercase Greek letter (ordinary).

The following symbols are most often used in plain text but LaTeX provides versions to use in mathematical text.

\mathdollar
     Dollar sign in math mode: $.

\mathparagraph
     Paragraph sign (pilcrow) in math mode,.

\mathsection
     Section sign in math mode.

\mathsterling
     Sterling sign in math mode: £.

\mathunderscore
     Underscore in math mode: _.

Blackboard bold
---------------

Synopsis:

     \usepackage{amssymb}   % in preamble
       ...
     \mathbb{UPPERCASE-LETTER}

Provide blackboard bold symbols, sometimes also known as doublestruck letters, used to denote number sets such as the natural numbers, the integers, etc.

Here

     \( \forall n \in \mathbb{N}, n^2 \geq 0 \)

the \mathbb{N} gives blackboard bold symbol representing the natural numbers.

If you use other than an uppercase letter then you do not get an error but you get strange results, including unexpected characters.

There are packages that give access to symbols other than just the capital letters; look on CTAN.

Calligraphic
------------

Synopsis:

     \mathcal{UPPERCASE-LETTERS}

Use a script-like font.

In this example the graph identifier is output in a cursive font.

     Let the graph be \( \mathcal{G} \).

If you use something other than an uppercase letter then you do not get an error.  Instead you get unexpected output.  For instance, \mathcal{g} outputs a close curly brace symbol, while \mathcal{+} outputs a plus sign.

\boldmath & \unboldmath
-----------------------

Synopsis (used in paragraph mode or LR mode):

     \boldmath \( MATH \)

or

     \unboldmath \( MATH \)

Declarations to change the letters and symbols in MATH to be in a bold font, or to countermand that and bring back the regular (non-bold) default. They must be used when not in math mode or display math mode (see Modes). Both commands are fragile (see \protect).

In this example each \boldmath command takes place inside an \mbox,

     we have $\mbox{\boldmath \( v \)} = 5\cdot\mbox{\boldmath \( u \)$}$

which means \boldmath is only called in a text mode, here LR mode, and explains why LaTeX must switch to math mode to set v and u.

If you use either command inside math mode, as with Trouble: \( \boldmath x \), then you get something like LaTeX Font Warning: Command \boldmath invalid in math mode on input line 11 and LaTeX Font Warning: Command \mathversion invalid in math mode on input line 11.

There are many issues with \boldmath.  New documents should use the bm package provided by the LaTeX Project team.  A complete description is outside the scope of this document (see the full documentation on CTAN) but even this small example

     \usepackage{bm}   % in preamble
     ...
     we have $\bm{v} = 5\cdot\bm{u}$

shows that it is an improvement over \boldmath.

Dots, horizontal or vertical
----------------------------

Ellipses are the three dots (usually three) indicating that a pattern continues.

     \begin{array}{cccc}
       a_{0,0}    &a_{0,1}   &a_{0,2} &\ldots \\
       a_{1,0}    &\ddots                     \\
       \vdots
     \end{array}

LaTeX provides these.

\cdots
     Horizontal ellipsis with the dots raised to the center of the line, as in.  Used as: \( a_0\cdot a_1\cdots a_{n-1}
     \).

\ddots
     Diagonal ellipsis,.  See the above array example for a usage.

\ldots
     Ellipsis on the baseline,.  Used as: \(
     x_0,\ldots x_{n-1} \).  Another example is the above array example. A synonym is \mathellipsis.  A synonym from the amsmath package is \hdots.

     You can also use this command outside of mathematical text, as in The gears, brakes, \ldots{} are all broken.  (In a paragraph mode or LR mode a synonym for \ldots is \dots.)

\vdots
     Vertical ellipsis,.  See the above array example for a usage.

The amsmath package has the command \dots to semantically mark up ellipses.  This example produces two different-looking outputs for the first two uses of the \dots command.

     \usepackage{amsmath}  % in preamble
       ...
     Suppose that \( p_0, p_1, \dots, p_{n-1} \) lists all of the primes.
     Observe that \( p_0\cdot p_1 \dots \cdot p_{n-1} +1 \) is not a
       multiple of any \( p_i \).
     Conclusion: there are infinitely many primes \( p_0, p_1, \dotsc \).

In the first line LaTeX looks to the comma following \dots to determine that it should output an ellipsis on the baseline.  The second line has a \cdot following \dots so LaTeX outputs an ellipsis that is on the math axis, vertically centered.  However, the third usage has no follow-on character so you have to tell LaTeX what to do.  You can use one of the commands: \dotsc if you need the ellipsis appropriate for a comma following, \dotsb if you need the ellipses that fits when the dots are followed by a binary operator or relation symbol, \dotsi for dots with integrals, or \dotso for others.

Math functions
==============

These commands produce roman function names in math mode with proper spacing.

\arccos
     Inverse cosine

\arcsin
     Inverse sine

\arctan
     Inverse tangent

\arg
     Angle between the real axis and a point in the complex plane

\bmod
     Binary modulo operator, used as in \( 5\bmod 3=2 \)

\cos
     Cosine

\cosh
     Hyperbolic cosine

\cot
     Cotangent

\coth
     Hyperbolic cotangent

\csc
     Cosecant

\deg
     Degrees

\det
     Determinant

\dim
     Dimension

\exp
     Exponential

\gcd
     Greatest common divisor

\hom
     Homomorphism

\inf
     Infinum

\ker
     Kernel

\lg
     Base 2 logarithm

\lim
     Limit

\liminf
     Limit inferior

\limsup
     Limit superior

\ln
     Natural logarithm

\log
     Logarithm

\max
     Maximum

\min
     Minimum

\pmod
     Parenthesized modulus, as used in \( 5\equiv 2\pmod 3 \)

\Pr
     Probability

\sec
     Secant

\sin
     Sine

\sinh
     Hyperbolic sine

\sup