# Logical structure

LaTeX provides ways to concentrate on the logical structure of your document, as well as the ability to directly set the appearance. Most of the time, it’s much better to use methods that focus on structure, as that makes it easy to reuse or alter appearance when you have to.

## A first example

We’ll start with an example contrasting one of the most common logical markup commands in LaTeX, \emph, with simply making something italic. (In print, that’s usually how things are emphasised.)

\documentclass{article}
\begin{document}
Some text with \emph{emphasis and \emph{nested} content}.

Some text in \textit{italic and \textit{nested} content}.
\end{document}


You can probably guess that \textit is a command to make text italic, but it always makes things italic, so it doesn’t work for nested material. See how \emph does know about nesting. There are also places where the emphasis isn’t the same as italic; for example, in presentations color is usually a better option. With logical markup, we don’t have to worry about that detail in the body of the document.

We will look at manual formatting later, but for the moment we’ll add \textbf to commands we know: it makes text bold.

## Sectioning commands

You probably have used a word processor, where to start a section most people enter the title text then simply make it bigger and bold, and follow it with a new line. In LaTeX, using logical markup is actually easier than doing the formatting by hand; we can use the \section command. This handles the font changes, vertical space, etc., and keeps the output uniform throughout the document.

\documentclass{article}
\begin{document}
Hey world!

This is a first document.

\section{Title of the first section}

Text of material in the first section

Second paragraph.

\subsection{Subsection of the first section}

Text of material in the subsection.

\section{Second section}

Text of the second section.

\end{document}


Using the standard article setup, LaTeX numbers the sections and subsections and includes the titles in boldface. We’ll think a bit about changing design in the next lesson.

LaTeX can divide up documents into quite a few levels

• \chapter (but we need \documentclass{book} or \documentclass{report} for this)
• \section
• \subsection
• \subsubsection

We can go further: the next one ‘down’ is \paragraph, but almost always that’s too much ‘detail’ in sections. (Yes, \paragraph is a section command, not a way to start a new paragraph!)

You might wonder about the title of a document. There are some special commands for that, but not all documents use them, so we’ve covered that in the parallel extra lesson.

## Lists

The other very common place you’ll want logical markup is writing lists. There are two common types of list built in to LaTeX.

\documentclass{article}
\begin{document}

Ordered
\begin{enumerate}
\item An entry
\item Another One
\item Wow! Three entries
\end{enumerate}

Unordered
\begin{itemize}
\item An entry
\item Another One
\item Wow! Three entries
\end{itemize}

\end{document}


Notice that we use \item to start each entry, and that the marker used for each type of list is added automatically.

## Exercises

Experiment with different sectioning levels. Try using \documentclass{report} instead of \documentclass{article} and adding \chapter commands. How do they look? Try out \paragraph and (even) \subparagraph to see they work: by default, they don’t add numbers.

Make some lists, and nest one list inside another. How does the format of the numbers or markers change? You can only go to four levels with standard LaTeX, but more than four nested lists tends to be a bad sign anyway!

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