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</head>

<body id="top" lang="en">
<a name="Sectioning" class="anchor"></a>
<a name="Sectioning-1" class="anchor"></a>
<h2 class="chapter">Sectioning</h2>

<a name="index-sectioning-commands" class="anchor"></a>
<a name="index-part" class="anchor"></a>
<a name="index-chapter" class="anchor"></a>
<a name="index-section" class="anchor"></a>
<a name="index-subsection" class="anchor"></a>
<a name="index-paragraph" class="anchor"></a>
<a name="index-subparagraph" class="anchor"></a>
<a name="index-_005cpart" class="anchor"></a>
<a name="index-_005cchapter" class="anchor"></a>
<a name="index-_005csection" class="anchor"></a>
<a name="index-_005csubsection" class="anchor"></a>
<a name="index-_005cparagraph" class="anchor"></a>
<a name="index-_005csubparagraph" class="anchor"></a>

<p>Structure your text into divisions: parts, chapters, sections, etc.  All
sectioning commands have the same form, one of:
</p>
<div class="example">
<pre class="example"><var>sectioning-command</var>{<var>title</var>}
<var>sectioning-command</var>*{<var>title</var>}
<var>sectioning-command</var>[<var>toc-title</var>]{<var>title</var>}
</pre></div>

<p>For instance, declare the start of a subsection as with
<code>\subsection{Motivation}</code>.
</p>
<p>The table has each <var>sectioning-command</var> in LaTeX.  All are
available in all of LaTeX&rsquo;s standard document classes <code>book</code>,
<code>report</code>, and&nbsp;<code>article</code>, except that <code>\chapter</code> is
not available in <code>article</code>.
</p>
<table>
<thead><tr><th width="25%">Sectioning unit</th><th width="25%">Command</th><th width="40%">Level</th></tr></thead>
<tr><td width="25%">Part</td><td width="25%"><code>\part</code></td><td width="40%">-1 (<code>book</code>, <code>report</code>), 0 (<code>article</code>)</td></tr>
<tr><td width="25%">Chapter</td><td width="25%"><code>\chapter</code></td><td width="40%">0</td></tr>
<tr><td width="25%">Section</td><td width="25%"><code>\section</code></td><td width="40%">1</td></tr>
<tr><td width="25%">Subsection</td><td width="25%"><code>\subsection</code></td><td width="40%">2</td></tr>
<tr><td width="25%">Subsubsection</td><td width="25%"><code>\subsubsection</code></td><td width="40%">3</td></tr>
<tr><td width="25%">Paragraph</td><td width="25%"><code>\paragraph</code></td><td width="40%">4</td></tr>
<tr><td width="25%">Subparagraph</td><td width="25%"><code>\subparagraph</code></td><td width="40%">5</td></tr>
</table>

<a name="index-_002a_002dform-of-sectioning-commands" class="anchor"></a>
<p>All these commands have a <code>*</code>-form that prints <var>title</var> 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 <code>article</code> .  The
input <code>\appendix\section{Appendix}</code> gives the output &lsquo;<samp>A
Appendix</samp>&rsquo; (see <a href="#g_t_005cappendix">\appendix</a>).  You can lose the numbering&nbsp;&lsquo;<samp>A</samp>&rsquo;
by instead entering <code>\section*{Appendix}</code> (articles often omit a
table of contents and have simple page headers so the other differences
from the <code>\section</code> command may not matter).
</p>
<p>The section title <var>title</var> 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 <a href="latex2e_18.html#Page-styles">Page styles</a>).  You may not want the same text in these
places as in the main text.  All of these commands have an optional
argument <var>toc-title</var> for these other places.
</p>
<p>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&rsquo;s <var>level</var> is less than or equal to the value of the counter
<code>secnumdepth</code> then the titles for this sectioning command will be
numbered (see <a href="#Sectioning_002fsecnumdepth">Sectioning/secnumdepth</a>).  And, if <var>level</var> is less
than or equal to the value of the counter <code>tocdepth</code> then the table
of contents will have an entry for this sectioning unit
(see <a href="#Sectioning_002ftocdepth">Sectioning/tocdepth</a>).
</p>
<p>LaTeX expects that before you have a <code>\subsection</code> you will have
a <code>\section</code> and, in a book, that before a <code>\section</code> you will
have a <code>\chapter</code>.  Otherwise you can get a something like a
subsection numbered &lsquo;<samp>3.0.1</samp>&rsquo;.
</p>
<p>Two counters relate to the appearance of sectioning commands.
</p>
<dl compact="compact">
<dt><code>secnumdepth</code>
<a name="index-secnumdepth" class="anchor"></a>
</dt>
<dd><a name="index-secnumdepth-counter" class="anchor"></a>
<a name="index-section-numbers_002c-printing" class="anchor"></a>
<a name="sectioning-secnumdepth" class="anchor"></a><a name="Sectioning_002fsecnumdepth" class="anchor"></a><p>Controls which sectioning commands are
numbered.  Suppress numbering of sectioning at any depth greater than
<var>level</var> <code>\setcounter{secnumdepth}{<var>level</var>}</code>
(see <a href="latex2e_13.html#g_t_005csetcounter">\setcounter</a>).  See the above table for the level numbers.  For
instance, if the <code>secnumdepth</code> is 1 in an <code>article</code> then a
<code>\section{Introduction}</code> command will produce output like &lsquo;<samp>1
Introduction</samp>&rsquo; while <code>\subsection{Discussion}</code> will produce output
like &lsquo;<samp>Discussion</samp>&rsquo;, without the number. LaTeX&rsquo;s default
<code>secnumdepth</code> is&nbsp;3 in <samp>article</samp> class and &nbsp;2 in the
<samp>book</samp> and <samp>report</samp> classes.
</p>
</dd>
<dt><code>tocdepth</code>
<a name="index-tocdepth" class="anchor"></a>
</dt>
<dd><a name="index-tocdepth-counter" class="anchor"></a>
<a name="index-table-of-contents_002c-sectioning-numbers-printed" class="anchor"></a>
<a name="sectioning-tocdepth" class="anchor"></a><a name="Sectioning_002ftocdepth" class="anchor"></a><p>Controls which sectioning units are listed in the table of contents.
The setting <code>\setcounter{tocdepth}{<var>level</var>}</code> makes the
sectioning units at <var>level</var> be the smallest ones listed
(see <a href="latex2e_13.html#g_t_005csetcounter">\setcounter</a>).  See the above table for the level numbers.  For
instance, if <code>tocdepth</code> is&nbsp;1 then the table of contents will
list sections but not subsections.  LaTeX&rsquo;s default
<code>secnumdepth</code> is&nbsp;3 in <samp>article</samp> class and &nbsp;2 in the
<samp>book</samp> and <samp>report</samp> classes.
</p>
</dd>
</dl>



<hr>
<a name="g_t_005cpart" class="anchor"></a>
<a name="g_t_005cpart-1" class="anchor"></a>
<h3 class="section"><code>\part</code></h3>

<a name="index-_005cpart-1" class="anchor"></a>
<a name="index-part-1" class="anchor"></a>
<a name="index-sectioning_002c-part" class="anchor"></a>

<p>Synopsis, one of:
</p>
<div class="example">
<pre class="example">\part{<var>title</var>}
\part*{<var>title</var>}
\part[<var>toc-title</var>]{<var>title</var>}
</pre></div>

<p>Start a document part.  The standard LaTeX classes <code>book</code>,
<code>report</code>, and <code>article</code>, all have this command.
</p>
<p>This produces a document part, in a book.
</p>
<div class="example">
<pre class="example">\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.
</pre></div>

<p>In each standard class the <code>\part</code> command outputs a part number
such as &lsquo;<samp>Part I</samp>&rsquo;, alone on its line, in boldface, and in large
type.  Then LaTeX outputs <var>title</var>, also alone on its line, in
bold and in even larger type.  In class <code>book</code>, 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 <code>report</code> it is again alone on a page, but
LaTeX won&rsquo;t force it onto an odd-numbered page.  In an <code>article</code>
LaTeX does not put it on a fresh page, but instead outputs the part
number and part title onto the main document page.
</p>
<p>The <code>*</code>&nbsp;form shows <var>title</var> 
but it does not show the part number, does not increment the
<code>part</code> counter, and produces no table of contents entry.
</p>
<p>The optional argument <var>toc-title</var> will appear as the part title in
the table of contents (see <a href="latex2e_25.html#Table-of-contents-etc_002e">Table of contents etc.</a>) and in running
headers (see <a href="latex2e_18.html#Page-styles">Page styles</a>).  If it is not present then <var>title</var>
will be there.  This example puts a line break in <var>title</var> but leaves
out the break in the table of contents.
</p>
<div class="example">
<pre class="example">\part[Up from the bottom; my life]{Up from the bottom\\ my life}
</pre></div>

<p>For determining which sectional units are numbered and which appear in
the table of contents, the level number of a part is&nbsp;-1
(see <a href="#Sectioning_002fsecnumdepth">Sectioning/secnumdepth</a> and see <a href="#Sectioning_002ftocdepth">Sectioning/tocdepth</a>).
</p>
<a name="index-package_002c-indentfirst" class="anchor"></a>
<a name="index-indentfirst-package" class="anchor"></a>

<p>In the class <code>article</code>, if a paragraph immediately follows the part
title then it is not indented.  To get an indent you can use the package
<samp>indentfirst</samp>.
</p>
<a name="index-package_002c-titlesec" class="anchor"></a>
<a name="index-titlesec-package" class="anchor"></a>

<p>One package to change the behavior of <code>\part</code> is <samp>titlesec</samp>.
See its documentation on CTAN.
</p>

<hr>
<a name="g_t_005cchapter" class="anchor"></a>
<a name="g_t_005cchapter-1" class="anchor"></a>
<h3 class="section"><code>\chapter</code></h3>

<a name="index-_005cchapter-1" class="anchor"></a>
<a name="index-chapter-1" class="anchor"></a>

<p>Synopsis, one of:
</p>
<div class="example">
<pre class="example">\chapter{<var>title</var>}
\chapter*{<var>title</var>}
\chapter[<var>toc-title</var>]{<var>title</var>}
</pre></div>

<p>Start a chapter.  The standard LaTeX classes <code>book</code> and
<code>report</code> have this command but <code>article</code> does not.
</p>
<p>This produces a chapter.
</p>
<div class="example">
<pre class="example">\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.
</pre></div>

<p>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 &lsquo;<samp>Chapter 1</samp>&rsquo; in large boldface type (the size is
<code>\huge</code>).  It then puts <var>title</var> on a fresh line, in boldface
type that is still larger (size <code>\Huge</code>).  It also increments the
<code>chapter</code> counter, adds an entry to the table of contents
(see <a href="latex2e_25.html#Table-of-contents-etc_002e">Table of contents etc.</a>), and sets the running header
information (see <a href="latex2e_18.html#Page-styles">Page styles</a>).
</p>
<p>The <code>*</code>&nbsp;form shows <var>title</var> on a fresh line, in boldface.
But it does not show the chapter number, does not increment the
<code>chapter</code> counter, produces no table of contents entry, and does
not affect the running header.  (If you use the page style
<code>headings</code> in a two-sided document then the header will be from the
prior chapter.)  This example illustrates.
</p>
<div class="example">
<pre class="example">\chapter*{Preamble}
</pre></div>

<p>The optional argument <var>toc-title</var> will appear as the chapter title
in the table of contents (see <a href="latex2e_25.html#Table-of-contents-etc_002e">Table of contents etc.</a>) and in
running headers (see <a href="latex2e_18.html#Page-styles">Page styles</a>).  If it is not present then
<var>title</var> will be there.  This shows the full name in the chapter
title,
</p>
<div class="example">
<pre class="example">\chapter[Weyl]{Hermann Klaus Hugo (Peter) Weyl (1885--1955)}
</pre></div>

<p>but only &lsquo;<samp>Weyl</samp>&rsquo; on the contents page.  This puts a line break in
the title but that doesn&rsquo;t work well with running headers so it omits
the break in the contents
</p>
<div class="example">
<pre class="example">\chapter[Given it all\\ my story]{Given it all\\ my story}
</pre></div>

<p>For determining which sectional units are numbered and which appear in
the table of contents, the level number of a chapter is&nbsp;0
(see <a href="#Sectioning_002fsecnumdepth">Sectioning/secnumdepth</a> and see <a href="#Sectioning_002ftocdepth">Sectioning/tocdepth</a>).
</p>
<a name="index-package_002c-indentfirst-1" class="anchor"></a>
<a name="index-indentfirst-package-1" class="anchor"></a>

<p>The paragraph that follows the chapter title is not indented, as is a
standard typographical practice.  To get an indent use the package
<samp>indentfirst</samp>.
</p>
<p>You can change what is shown for the chapter number.  To change it to
something like &lsquo;<samp>Lecture 1</samp>&rsquo;, put in the preamble either
<code>\renewcommand{\chaptername}{Lecture}</code> or this
(see <a href="latex2e_12.html#g_t_005cmakeatletter-_0026-_005cmakeatother">\makeatletter &amp; \makeatother</a>).
</p>
<div class="example">
<pre class="example">\makeatletter
\renewcommand{\@chapapp}{Lecture}
\makeatother
</pre></div>

<a name="index-package_002c-babel" class="anchor"></a>
<a name="index-babel-package" class="anchor"></a>

<p>To make this change because of the primary language for
the document, see the package <samp>babel</samp>.
</p>
<p>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&nbsp;<a href="latex2e_10.html#g_t_005cclearpage-_0026-_005ccleardoublepage">\clearpage &amp; \cleardoublepage</a>.
</p>
<a name="index-package_002c-titlesec-1" class="anchor"></a>
<a name="index-titlesec-package-1" class="anchor"></a>

<p>To change the behavior of the <code>\chapter</code> 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
<samp>titlesec</samp>.  See its documentation, but the example below gives a
sense of what it can do.
</p>
<div class="example">
<pre class="example">\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
</pre></div>

<p>This omits the chapter number &lsquo;<samp>Chapter 1</samp>&rsquo; from the page but unlike
<code>\chapter*</code> it keeps the chapter in the table of contents and the
running headers.
</p>

<hr>
<a name="g_t_005csection" class="anchor"></a>
<a name="g_t_005csection-1" class="anchor"></a>
<h3 class="section"><code>\section</code></h3>

<a name="index-_005csection-1" class="anchor"></a>
<a name="index-section-1" class="anchor"></a>

<p>Synopsis, one of:
</p>
<div class="example">
<pre class="example">\section{<var>title</var>}
\section*{<var>title</var>}
\section[<var>toc-title</var>]{<var>title</var>}
</pre></div>

<p>Start a section.  The standard LaTeX classes <code>article</code>,
<code>book</code>, and <code>report</code> all have this command.
</p>
<p>This produces a section.
</p>
<div class="example">
<pre class="example">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.
</pre></div>

<p>For the standard LaTeX classes <code>book</code> and <code>report</code> the
default output is like &lsquo;<samp>1.2 <var>title</var></samp>&rsquo; (for chapter&nbsp;1,
section&nbsp;2), alone on its line and flush left, in boldface and a
larger type (the type size is <code>\Large</code>).  The same holds in
<code>article</code> except that there are no chapters in that class so it
looks like &lsquo;<samp>2 <var>title</var></samp>&rsquo;.
</p>
<p>The <code>*</code>&nbsp;form shows <var>title</var>.
But it does not show the section number, does not increment the
<code>section</code> counter, produces no table of contents entry, and does
not affect the running header.  (If you use the page style
<code>headings</code> in a two-sided document then the header will be from the
prior section.)
</p>
<p>The optional argument <var>toc-title</var> will appear as the section title
in the table of contents (see <a href="latex2e_25.html#Table-of-contents-etc_002e">Table of contents etc.</a>) and in
running headers (see <a href="latex2e_18.html#Page-styles">Page styles</a>).  If it is not present then
<var>title</var> will be there.  This shows the full name in the title of the
section,
</p>
<div class="example">
<pre class="example">\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.}
</pre></div>

<p>but only &lsquo;<samp>Elizabeth II</samp>&rsquo; on the contents page and in the headers.
This has a line break in <var>title</var> but that does not work with headers
so it is omitted from the contents and headers.
</p>
<div class="example">
<pre class="example">\section[Truth is, I cheated; my life story]{Truth is,
  I cheated\\my life story}
</pre></div>

<p>For determining which sectional units are numbered and which appear in
the table of contents, the level number of a section is&nbsp;1
(see <a href="#Sectioning_002fsecnumdepth">Sectioning/secnumdepth</a> and see <a href="#Sectioning_002ftocdepth">Sectioning/tocdepth</a>).
</p>
<a name="index-package_002c-indentfirst-2" class="anchor"></a>
<a name="index-indentfirst-package-2" class="anchor"></a>

<p>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 <samp>indentfirst</samp>.
</p>
<a name="index-package_002c-titlesec-2" class="anchor"></a>
<a name="index-titlesec-package-2" class="anchor"></a>

<p>In general, to change the behavior of the <code>\section</code> command, there
are a number of options.  One is the <code>\@startsection</code> command
(see <a href="#g_t_005c_0040startsection">\@startsection</a>).  There are also many packages on CTAN that
address this, including <samp>titlesec</samp>.  See the documentation but the
example below gives a sense of what they can do.
</p>
<div class="example">
<pre class="example">\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]
</pre></div>

<p>That puts the section number in the margin.
</p>

<hr>
<a name="g_t_005csubsection" class="anchor"></a>
<a name="g_t_005csubsection-1" class="anchor"></a>
<h3 class="section"><code>\subsection</code></h3>

<a name="index-_005csubsection-1" class="anchor"></a>
<a name="index-subsection-1" class="anchor"></a>

<p>Synopsis, one of:
</p>
<div class="example">
<pre class="example">\subsection{<var>title</var>}
\subsection*{<var>title</var>}
\subsection[<var>toc-title</var>]{<var>title</var>}
</pre></div>

<p>Start a subsection.  The standard LaTeX classes <code>article</code>,
<code>book</code>, and <code>report</code> all have this command.
</p>
<p>This produces a subsection.
</p>
<div class="example">
<pre class="example">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.
</pre></div>

<p>For the standard LaTeX classes <code>book</code> and <code>report</code> the
default output is like &lsquo;<samp>1.2.3 <var>title</var></samp>&rsquo; (for chapter&nbsp;1,
section&nbsp;2, subsection&nbsp;3), alone on its line and flush left, in
boldface and a larger type (the type size is <code>\large</code>).  The same
holds in <code>article</code> except that there are no chapters in that class
so it looks like &lsquo;<samp>2.3 <var>title</var></samp>&rsquo;.
</p>
<p>The <code>*</code>&nbsp;form shows <var>title</var>.
But it does not show the section number, does not increment the
<code>section</code> counter, and produces no table of contents entry.
</p>
<p>The optional argument <var>toc-title</var> will appear as the section title
in the table of contents (see <a href="latex2e_25.html#Table-of-contents-etc_002e">Table of contents etc.</a>).  If it is
not present then <var>title</var> will be there.  This shows the full name in
the title of the section,
</p>
<div class="example">
<pre class="example">\subsection[$\alpha,\beta,\gamma$ paper]{\textit{The Origin of
  Chemical Elements} by R.A.~Alpher, H.~Bethe, and G.~Gamow}
</pre></div>

<p>but only &lsquo;<samp>&#x03B1;,&#x03B2;,&#x03B3;
paper</samp>&rsquo; on the contents page.
</p>
<p>For determining which sectional units are numbered and which appear in
the table of contents, the level number of a subsection is&nbsp;2
(see <a href="#Sectioning_002fsecnumdepth">Sectioning/secnumdepth</a> and see <a href="#Sectioning_002ftocdepth">Sectioning/tocdepth</a>).
</p>
<a name="index-package_002c-indentfirst-3" class="anchor"></a>
<a name="index-indentfirst-package-3" class="anchor"></a>

<p>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 <samp>indentfirst</samp>.
</p>
<a name="index-package_002c-titlesec-3" class="anchor"></a>
<a name="index-titlesec-package-3" class="anchor"></a>

<p>There are a number of ways to change the behavior of the
<code>\subsection</code> command.  One is the <code>\@startsection</code> command
(see <a href="#g_t_005c_0040startsection">\@startsection</a>).  There are also many packages on CTAN that
address this, including <samp>titlesec</samp>.  See the documentation but the
example below gives a sense of what they can do.
</p>
<div class="example">
<pre class="example">\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
</pre></div>

<p>That puts the subsection number and <var>title</var> in the first line of
text.
</p>

<hr>
<a name="g_t_005csubsubsection-_0026-_005cparagraph-_0026-_005csubparagraph" class="anchor"></a>

<a name="g_t_005csubsubsection_002c-_005cparagraph_002c-_005csubparagraph" class="anchor"></a>
<h3 class="section"><code>\subsubsection</code>, <code>\paragraph</code>, <code>\subparagraph</code></h3>

<a name="index-_005csubsubsection" class="anchor"></a>
<a name="index-subsubsection" class="anchor"></a>
<a name="index-_005cparagraph-1" class="anchor"></a>
<a name="index-paragraph-1" class="anchor"></a>
<a name="index-_005csubparagraph-1" class="anchor"></a>
<a name="index-subparagraph-1" class="anchor"></a>

<p>Synopsis, one of:
</p>
<div class="example">
<pre class="example">\subsubsection{<var>title</var>}
\subsubsection*{<var>title</var>}
\subsubsection[<var>toc-title</var>]{<var>title</var>}
</pre></div>

<p>or one of:
</p>
<div class="example">
<pre class="example">\paragraph{<var>title</var>}
\paragraph*{<var>title</var>}
\paragraph[<var>toc-title</var>]{<var>title</var>}
</pre></div>

<p>or one of:
</p>
<div class="example">
<pre class="example">\subparagraph{<var>title</var>}
\subparagraph*{<var>title</var>}
\subparagraph[<var>toc-title</var>]{<var>title</var>}
</pre></div>

<p>Start a subsubsection, paragraph, or subparagraph.  The standard
LaTeX classes <code>article</code>, <code>book</code>, and <code>report</code> all have
these commands, although they are not commonly used.
</p>
<p>This produces a subsubsection.
</p>
<div class="example">
<pre class="example">\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.
</pre></div>

<p>The default output of each of the three does not change over the
standard LaTeX classes <code>article</code>, <code>book</code>, and
<code>report</code>.  For <code>\subsubsection</code> the <var>title</var> is alone on
its line, in boldface and normal size type.  For <code>\paragraph</code> the
<var>title</var> is inline with the text, not indented, in boldface and
normal size type.  For <code>\subparagraph</code> the <var>title</var> is inline
with the text, with a paragraph indent, in boldface and normal size type
(Because an <code>article</code> has no chapters its subsubsections are
numbered and so it looks like &lsquo;<samp>1.2.3 <var>title</var></samp>&rsquo;, for
section&nbsp;1, subsection&nbsp;2, and subsubsection&nbsp;3.  The other
two divisions are not numbered.)
</p>
<p>The <code>*</code>&nbsp;form shows <var>title</var>.  But it does not increment the
associated counter and produces no table of contents entry (and does not
show the number for <code>\subsubsection</code>).
</p>
<p>The optional argument <var>toc-title</var> will appear as the division title
in the table of contents (see <a href="latex2e_25.html#Table-of-contents-etc_002e">Table of contents etc.</a>).  If it is
not present then <var>title</var> will be there.
</p>
<p>For determining which sectional units are numbered and which appear in
the table of contents, the level number of a subsubsection is&nbsp;3, of
a paragraph is&nbsp;4, and of a subparagraph is&nbsp;5
(see <a href="#Sectioning_002fsecnumdepth">Sectioning/secnumdepth</a> and see <a href="#Sectioning_002ftocdepth">Sectioning/tocdepth</a>).
</p>
<a name="index-package_002c-indentfirst-4" class="anchor"></a>
<a name="index-indentfirst-package-4" class="anchor"></a>

<p>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 <samp>indentfirst</samp>.
</p>
<a name="index-package_002c-titlesec-4" class="anchor"></a>
<a name="index-titlesec-package-4" class="anchor"></a>

<p>There are a number of ways to change the behavior of the these commands.
One is the <code>\@startsection</code> command (see <a href="#g_t_005c_0040startsection">\@startsection</a>).
There are also many packages on CTAN that address this, including
<samp>titlesec</samp>.  See the documentation on CTAN.
</p>

<hr>
<a name="g_t_005cappendix" class="anchor"></a>

<a name="g_t_005cappendix-1" class="anchor"></a>
<h3 class="section"><code>\appendix</code></h3>

<a name="index-_005cappendix" class="anchor"></a>
<a name="index-appendix" class="anchor"></a>
<a name="index-appendices" class="anchor"></a>

<p>Synopsis:
</p>
<div class="example">
<pre class="example">\appendix
</pre></div>

<p>This does not directly produce any output.  But in a book or report it
declares that subsequent <code>\chapter</code> commands start an appendix.  In
an article it does the same, for <code>\section</code> commands.  It also
resets the <code>chapter</code> and <code>section</code> counters to&nbsp;0 in a
book or report, and in an article resets the <code>section</code> and
<code>subsection</code> counters.
</p>
<p>In this book
</p>
<div class="example">
<pre class="example">\chapter{One}  ...
\chapter{Two}  ...
 ...
\appendix
\chapter{Three}  ...
\chapter{Four}  ...
</pre></div>

<p>the first two will generate output numbered &lsquo;<samp>Chapter 1</samp>&rsquo; and
&lsquo;<samp>Chapter 2</samp>&rsquo;.  After the <code>\appendix</code> the numbering will be
&lsquo;<samp>Appendix A</samp>&rsquo; and &lsquo;<samp>Appendix B</samp>&rsquo;.  See <a href="latex2e_29.html#Larger-book-template">Larger book template</a>
for another example.
</p>
<a name="index-package_002c-appendix" class="anchor"></a>
<a name="index-appendix-package" class="anchor"></a>
<p>The <samp>appendix</samp> package adds the command
<code>\appendixpage</code> to put a separate &lsquo;<samp>Appendices</samp>&rsquo; in the document
body before the first appendix, and the command <code>\addappheadtotoc</code>
to do the same in the table of contents.  You can reset the name
&lsquo;<samp>Appendix</samp>&rsquo; with a command like
<code>\renewcommand{\appendixname}{Specification}</code>, as well as a
number of other features.  See the documentation on CTAN.
</p>

<hr>
<a name="g_t_005cfrontmatter-_0026-_005cmainmatter-_0026-_005cbackmatter" class="anchor"></a>

<a name="g_t_005cfrontmatter_002c-_005cmainmatter_002c-_005cbackmatter" class="anchor"></a>
<h3 class="section"><code>\frontmatter</code>, <code>\mainmatter</code>, <code>\backmatter</code></h3>

<a name="index-_005cfrontmatter" class="anchor"></a>
<a name="index-book_002c-front-matter" class="anchor"></a>
<a name="index-_005cmainmatter" class="anchor"></a>
<a name="index-book_002c-main-matter" class="anchor"></a>
<a name="index-_005cbackmatter" class="anchor"></a>
<a name="index-book_002c-back-matter" class="anchor"></a>
<a name="index-book_002c-end-matter" class="anchor"></a>

<p>Synopsis, one of:
</p>
<div class="example">
<pre class="example">\frontmatter
\mainmatter
\backmatter
</pre></div>

<p>Format a <code>book</code> class document differently according to which part
of the document is being produced.  All three commands are optional.
</p>
<p>Traditionally, a book&rsquo;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.
</p>
<p>The <code>\frontmatter</code> declaration makes the pages numbered in
lowercase roman, and makes chapters not numbered, although each
chapter&rsquo;s title appears in the table of contents; if you use other
sectioning commands here, use the <code>*</code>-version (see <a href="#Sectioning">Sectioning</a>).
The <code>\mainmatter</code> changes the behavior back to the expected
version, and resets the page number.  The <code>\backmatter</code> leaves the
page numbering alone but switches the chapters back to being not
numbered.  See <a href="latex2e_29.html#Larger-book-template">Larger book template</a> for an example using the three.
</p>

<hr>
<a name="g_t_005c_0040startsection" class="anchor"></a>
<a name="g_t_005c_0040startsection-1" class="anchor"></a>
<h3 class="section"><code>\@startsection</code></h3>

<a name="index-_005c_0040startsection" class="anchor"></a>
<a name="index-section_002c-redefining" class="anchor"></a>

<p>Synopsis:
</p>
<div class="example">
<pre class="example">\@startsection{<var>name</var>}{<var>level</var>}{<var>indent</var>}{<var>beforeskip</var>}{<var>afterskip</var>}{<var>style</var>}
</pre></div>

<p>Used to help redefine the behavior of commands that start sectioning
divisions such as <code>\section</code> or <code>\subsection</code>.
</p>
<p>Note that the <samp>titlesec</samp> package makes manipulation of sectioning
easier.  Further, while most requirements for sectioning commands can be
satisfied with <code>\@startsection</code>, some cannot.  For instance, in
the standard LaTeX <code>book</code> and <code>report</code> classes the commands
<code>\chapter</code> and <code>\report</code> are not constructed in this way.  To
make such a command you may want to use the <code>\secdef</code> command.
</p>
<p>Technically, <code>\@startsection</code> has the form
</p>
<div class="example">
<pre class="example">\@startsection{<var>name</var>}
  {<var>level</var>}
  {<var>indent</var>}
  {<var>beforeskip</var>}
  {<var>afterskip</var>}
  {<var>style</var>}*[<var>toctitle</var>]{<var>title</var>}
</pre></div>

<p>so that issuing
</p>
<div class="example">
<pre class="example">\renewcommand{\section}{\@startsection{<var>name</var>}
  {<var>level</var>}
  {<var>indent</var>}
  {<var>beforeskip</var>}
  {<var>afterskip</var>}
  {<var>style</var>}}
</pre></div>

<p>redefines <code>\section</code> to have the form
<code>\section*[<var>toctitle</var>]{<var>title</var>}</code> (here too, the
star&nbsp;<code>*</code> is optional).  See <a href="#Sectioning">Sectioning</a>.  This implies that
when you write a command like <code>\renewcommand{section}{...}</code>,
the <code>\@startsection{...}</code> must come last in the definition.  See
the examples below.
</p>
<dl compact="compact">
<dt><var>name</var></dt>
<dd><a name="startsection-name" class="anchor"></a><a name="g_t_005c_0040startsection_002fname" class="anchor"></a><p>Name of the counter used to number the sectioning header.  This counter
must be defined separately.  Most commonly this is either
<code>section</code>, <code>subsection</code>, or <code>paragraph</code>.  Although in
those cases the counter name is the same as the sectioning command
itself, you don&rsquo;t have to use the same name.
</p>
<p>Then <code>\the</code><var>name</var> displays the title number and
<code>\</code><var>name</var><code>mark</code> is for the page headers.  See the third
example below.
</p>
</dd>
<dt><var>level</var></dt>
<dd><a name="startsection-level" class="anchor"></a><a name="g_t_005c_0040startsection_002flevel" class="anchor"></a><p>An integer giving the depth of the sectioning command.
See <a href="#Sectioning">Sectioning</a> for the list of standard level numbers.
</p>
<p>If <var>level</var> is less than or equal to the value of the counter
<code>secnumdepth</code> then titles for this sectioning command will be
numbered (see <a href="#Sectioning_002fsecnumdepth">Sectioning/secnumdepth</a>).  For instance, if
<code>secnumdepth</code> is 1 in an <code>article</code> then the command
<code>\section{Introduction}</code> will produce output like &ldquo;1
Introduction&rdquo; while <code>\subsection{Discussion}</code> will produce
output like &ldquo;Discussion&rdquo;, without the number prefix.
</p>
<p>If <var>level</var> is less than or equal to the value of the counter
<var>tocdepth</var> then the table of contents will have an entry for this
sectioning unit (see <a href="#Sectioning_002ftocdepth">Sectioning/tocdepth</a>).  For instance, in an
<code>article</code>, if <var>tocdepth</var> is 1 then the table of contents will
list sections but not subsections.
</p>
</dd>
<dt><var>indent</var></dt>
<dd><a name="startsection-indent" class="anchor"></a><a name="g_t_005c_0040startsection_002findent" class="anchor"></a><p>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
<code>0pt</code>.  A negative indentation such as <code>-\parindent</code> will move
the title into the left margin.
</p>
</dd>
<dt><var>beforeskip</var></dt>
<dd><a name="startsection-beforeskip" class="anchor"></a><a name="g_t_005c_0040startsection_002fbeforeskip" class="anchor"></a><p>The absolute value of this length is the amount of vertical space that
is inserted before this sectioning unit&rsquo;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 <code>1pt plus 2pt minus 3pt</code>
is <code>-1pt plus -2pt minus -3pt</code>.)
</p>
<p>For example, if <var>beforeskip</var> is <code>-3.5ex plus -1ex minus -0.2ex</code>
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
<code>plus</code> and <code>minus</code>, is good practice here since it gives
LaTeX more flexibility in making up the page (see <a href="latex2e_14.html#Lengths">Lengths</a>).
</p>
<p>The full accounting of the vertical space between the baseline of the
line prior to this sectioning unit&rsquo;s header and the baseline of the
header is that it is the sum of the <code>\parskip</code> of the text font,
the <code>\baselineskip</code> of the title font, and the absolute value of
the <var>beforeskip</var>.  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.)
</p>
</dd>
<dt><var>afterskip</var></dt>
<dd><a name="startsection-afterskip" class="anchor"></a><a name="g_t_005c_0040startsection_002fafterskip" class="anchor"></a><p>This is a length.  If <var>afterskip</var> is non-negative then this is the
vertical space inserted after the sectioning unit&rsquo;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
<code>1pt plus 2pt minus 3pt</code> is <code>-1pt plus -2pt minus -3pt</code>.)
</p>
<p>As with <var>beforeskip</var>, using a rubber length, with <code>plus</code> and
<code>minus</code> components, is good practice here since it gives LaTeX
more flexibility in putting together the page.
</p>
<p>If <code>afterskip</code> is non-negative then the full accounting of the
vertical space between the baseline of the sectioning unit&rsquo;s header and
the baseline of the first line of the following paragraph is that it is
the sum of the <code>\parskip</code> of the title font, the
<code>\baselineskip</code> of the text font, and the value of <var>after</var>.
That space is typically rubber so it may stretch or shrink.  (Note that
because the sign of <code>afterskip</code> changes the sectioning unit
header&rsquo;s from standalone to run-in, you cannot use a negative
<code>afterskip</code> to cancel part of the <code>\parskip</code>.)
</p>
</dd>
<dt><var>style</var></dt>
<dd><a name="startsection-style" class="anchor"></a><a name="g_t_005c_0040startsection_002fstyle" class="anchor"></a><p>Controls the styling of the title.  See the examples below.  Typical
commands to use here are <code>\centering</code>, <code>\raggedright</code>,
<code>\normalfont</code>, <code>\hrule</code>, or <code>\newpage</code>.  The last command
in <var>style</var> may be one that takes one argument, such as
<code>\MakeUppercase</code> or <code>\fbox</code> that takes one argument.  The
section title will be supplied as the argument to this command. For
instance, setting <var>style</var> to <code>\bfseries\MakeUppercase</code> would
produce titles that are bold and uppercase.
</p></dd>
</dl>

<p>These are LaTeX&rsquo;s defaults for the first three sectioning units that
are defined with <code>\@startsection</code>, for the <samp>article</samp>,
<samp>book</samp>, and <samp>report</samp> classes.  For section, the <var>level</var> is
1, the <var>indent</var> is 0pt, the <var>beforeskip</var> is <code>-3.5ex
plus -1ex minus -0.2ex</code>, the <var>afterskip</var> is <code>2.3ex plus 0.2ex</code>,
and the <var>style</var> is <code>\normalfont\Large\bfseries</code>.  For
subsection, the <var>level</var> is 2, the <var>indent</var> is 0pt, the
<var>beforeskip</var> is <code>-3.25ex plus -1ex minus -0.2ex</code>, the
<var>afterskip</var> is <code>1.5ex plus 0.2ex</code>, and the <var>style</var> is
<code>\normalfont\large\bfseries</code>.  For subsubsection, the <var>level</var>
is 3, the <var>indent</var> is 0pt, the <var>beforeskip</var> is
<code>-3.25ex plus -1ex minus -0.2ex</code>, the <var>afterskip</var> is
<code>1.5ex plus 0.2ex</code>, and the <var>style</var> is
<code>\normalfont\normalsize\bfseries</code>.
</p>
<p>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 <code>\makeatletter</code> command and a
<code>\makeatother</code>.  (Probably the error message <code>You can't use
`\spacefactor' in vertical mode.</code>  means that you forgot this.)
See <a href="latex2e_12.html#g_t_005cmakeatletter-_0026-_005cmakeatother">\makeatletter &amp; \makeatother</a>.
</p>
<p>This will put section titles in large boldface type, centered.  It says
<code>\renewcommand</code> because LaTeX&rsquo;s standard classes have already
defined a <code>\section</code>.  For the same reason it does not define a
<code>section</code> counter, or the commands <code>\thesection</code> and
<code>\l@section</code>.
</p>
<div class="example">
<pre class="example">\renewcommand\section{%
  \@startsection{section}% <a href="#g_t_005c_0040startsection_002fname"><var>name</var></a>
    {1}% <a href="#g_t_005c_0040startsection_002flevel"><var>level</var></a>
    {0pt}% <a href="#g_t_005c_0040startsection_002findent"><var>indent</var></a>
    {-3.5ex plus -1ex minus -.2ex}% <a href="#g_t_005c_0040startsection_002fbeforeskip"><var>beforeskip</var></a>
    {2.3ex plus.2ex}% <a href="#g_t_005c_0040startsection_002fafterskip"><var>afterskip</var></a>
    {\centering\normalfont\Large\bfseries}% <a href="#g_t_005c_0040startsection_002fstyle"><var>style</var></a>
  }
</pre></div>

<p>This will put <code>subsection</code> titles in small caps type, inline with the paragraph.
</p>
<div class="example">
<pre class="example">\renewcommand\subsection{%
  \@startsection{subsection}%  <a href="#g_t_005c_0040startsection_002fname"><var>name</var></a>
    {2}% <a href="#g_t_005c_0040startsection_002flevel"><var>level</var></a>
    {0em}% <a href="#g_t_005c_0040startsection_002findent"><var>indent</var></a>
    {-1ex plus 0.1ex minus -0.05ex}% <a href="#g_t_005c_0040startsection_002fbeforeskip"><var>beforeskip</var></a>
    {-1em plus 0.2em}% <a href="#g_t_005c_0040startsection_002fafterskip"><var>afterskip</var></a>
    {\scshape}% <a href="#g_t_005c_0040startsection_002fstyle"><var>style</var></a>
  }
</pre></div>

<p>The prior examples redefined existing sectional unit title commands.
This defines a new one, illustrating the needed counter and macros to
display that counter.
</p>
<div class="example">
<pre class="example">\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
</pre></div>





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