Document Structure¶

Packages¶

Once LaTeX knows what kind of document you are working in, relevant packages should be loaded. The order of packages loaded can matter, particularly if they alter some of the same settings. In this case, the package loaded last usually gets the final say.

Packages are loaded with the \usepackage{thepackage} command. The usepackage command also takes an optional argument which allows for changing some settings on the package. For example, the geometry package allows margins to be set using this method. If you want your document to have margins of 1 inch rather than the default by loading the package with \usepackage[margin=1in]{geometry}.

More information on packages is included in the Packages page.

New Commands¶

New commands are declared with \newcommand{}{}, a command which has two mandatory arguments. The first argument specifies how the command is called, and the second are how LaTeX should interpret the command. Say we like the way \(\varepsilon\) looks better than \(\epsilon\), but don’t want to have to type \varepsilon every time. By using \newcommand{\e}{\varepsilon}, we can create \(\varepsilon\) by just typing \e.

The \newcommand{}{} also takes an optional argument which specifies the number of arguments. More information on new commands is available in the New Command lesson.

Formatting¶

Generally, the last part of the preamble should be formatting. Now that packages are loaded and new commands have been created, there are many options to fiddle with and none will be overridden by loading packages after specifying custom formatting. Everything in LaTeX can be customized. Fortunately, specifying the document class prevents declaring the base formatting from being necessary. Sometimes, packages allow for easier access to formatting, such as creating custom list levels and formatting. More information on formatting is in the formatting lesson.

Miscellaneous Actions¶

There are many, many more things that can be useful to have in the preamble. These include declaring new operators, having an external preamble (to act as a stylesheet or collection of common commands for many documents), and even creating new environments.

Sections, Subsections, and Subsubsections, Oh My!¶

LaTeX provides many commands which make it easy to organize the body of the document using headings. These built-in commands also automatically provide content for the table of contents (should you choose to have one).

The table of contents is placed in the document with the command \tableofcontents. Because of the way LaTeX handles document struture, it does not immediately reflect the changes made to the document upon typesetting. If you change something and want the table of contents to update correctly, just typeset the document twice.

The most common section command is \section{Section Name}, with “Section Name” replaced with whatever you want the section to be called. These can be further divided with \subsection{}, and \subsubsection{}. For document class article, these are generally the only ones you will need to use. If you are typesetting a book or a report, there is a heading level above section, \chapter{}. The largest section heading level is \part{}, and can be used in nearly any document.

You should start with the highest level your document needs and work your way down. For most documents, sections, subsection, and subsubsection will be sufficient.

There are \paragraph{} and \subparagraph{} commands. They allow paragraphs to have titles, and look like this:

\paragraph{Paragraphs}
I'm a paragraph!
\subparagraph{Hey, }
I'm just a subparagraph.

Using these commands to specify paragraphs is generally unnecessary since most documents don’t need to be this structured. A paragraph break can be specified by inserting a blank line between paragraphs. If you want to keep the paragraph heading styling, but want to start the paragraph on it’s own line, just insert a new line as so:

\paragraph{Another Paragraph} \hspace{0pt} \\
I started on a new line!

If you want a section/subsection/subsubsection to not have a number, insert an asterisk in the command as so: \section*{Unnumbered}.

Debugging and Testing¶

Sometimes, LaTeX gives obscure errors and references lines which don’t actually contain errors. This is because LaTeX usually doesn’t encounter the errors until it tries to piece together code, such as at the end of an environment, most commonly when writing math.

Putting \end{document} inside of an environment does cause an error itself. However, LaTeX will have processed all code up to that point so the original error will still cause an issue. This is because when LaTeX encounters \end, it will typeset everything up to that point. If the only error is that \end{document} is inside an environment, then \end{document} is before the error. If not, then \end{document} is after the error. This allows for a line-by-line search to find the bug.

Code Storage¶

Sometimes there is part of a document that doesn’t fit anywhere inside the document currently, but might later. Rather than deleting the code or storing it somewhere else, placing it after \end{document} allows for safe storage.

For larger projects, it is a better idea to learn and use version control so nothing valuable will be lost.