The Preamble

The preamble is the first section of your .tex file. It comes before the the text of the document itself.

The preamble always starts with the definition of a “document class”. This is where you tell \(\LaTeX\) what kind of document you’re writing: an article, a book, a letter… More on that later.

You can then continue specifying additional information and packages in the preamble.

The preamble is then followed by the document text, the actual “content” of your document.

The overall structure resembles this one:

\documentclass{class}
This is your preamble, where you can specify packages.
\begin{document}
This is your document. This is the text that will be shown on the output file.
\end{document}

Notice how we specify the document class: beginning with a \ backslash. You will find similar statements over and over in your code. These tell $\LaTeX$ that they’re not actual text, but rather some instructions or commands.

All the commands follow the same structure: \nameofcommand{option}. Commands can also appear within the document body, not only in the preamble. You can also include some additional parameters within square brackets.

Document Class

Let’s start your new document. First, we need to tell $\LaTeX$ that we’re going to write an article. Then, we write “Hello, world!” as our document text.

\documentclass{article} % Specifies that we're writing an article
\begin{document}
Hello, world!
\end{document}

If you now compile the document, you should see “Hello, world!” together with a page number at the bottom, which $\LaTeX$ automatically added for us since we used the article document class.

That’s because $\LaTeX$ uses the document class to infer the page and document layout that it should use.

There are many document classes available out there. Here’s a comprehensive list. In this tutorial, we will only use the article class.

In case you wanted to slightly modify an existing class, you may use any of the available parameters for that class. For instance, you can specify a different font size (the default is 10pt) or a different paper format (the default is letterpaper) for the article class: \documentclass[12pt,a4paper]{article}.

As you can see, you can specify these additional parameters within square brackets.

Packages

You can extend the functionalities of $\LaTeX$ by importing some packages in the preamble, similar to what you’d do with Python or R packages. However, contrary to those, most packages will be already installed by default - no need to download them manually¹. So, if you want to include a package, you only need to tell $\LaTeX$ that you want to use it.

Import packages in the preamble with the command: \usepackage[options]{packagename}.

For instance, if we wanted to add an equation to our document, we would need the amsmath package. This is a package from the American Mathematical Society designed to add features, facilitate writing formulas and improve the typographical quality of math equations.

So, our new code would look like this:

\documentclass{article} % Specifies that we're writing an article
\usepackage{amsmath} % Imports amsmath
\begin{document}
Hello, world!
This is an equation:
  \begin{equation}
    E_0 = mc^2
  \end{equation}
\end{document}

There are many packages for a great variety of purposes, like adding pictures, a bibliography, flowcharts, links, and so on. Most of the time, you will simply need to look up which one is the one you need for the specific purpose.

Tip

We provide a short list of the most important packages at the end of this tutorial.

The Body

Environments

You may have noticed some commands with \begin and \end statements in our code above. Actually, these are not commands. Instead, they define the so-called environments.

An environment is a section of your document where particular typesetting rules apply. Usually, you will have multiple environments in the same document. For instance, in our previous example, we’ve added the equation environment within our document environment.

Tip

Try adding an abstract environment to your article on your own, if you feel you’ve mastered $\LaTeX$ environments so far.

Warning

You may specify as many environments as you wish, nested into each other or in any sequential order. However, it is imperative to specify the document environment as the very first one. In other words, you cannot have any environment outside the document environment.

The Title Page

Let’s now add a title page to our article. This page will show the article title, the author and a date.

Add these to your preamble:

\title{My First \LaTeX{} Article}
\author{John Doe}
\date{January 1st, 2000}

Great! Now let’s build again our document and… Oh, wait. Why isn’t the title showing up?

That’s because we’ve only specified the information in the preamble. But we did not tell $\LaTeX$ where to show that information inside our document.

Therefore, we’ll also need to add the \maketitle command at the place you want the title to be printed, which is right after we begin the document environment in our case. If we wanted to make the title fill the entire first page, we may also add the command \newpage so that the article content starts from the second page.

\begin{document}
\maketitle
\newpage
Hello, world!
This is an equation:
  \begin{equation}
    E_0 = mc^2
  \end{equation}
\end{document}

Tip

Try building your document with and without the \newpage command to see how it effects the output.

Basic Formatting Options

A few formatting options that you’ll need to remember:

These backslashes\\will break the line.

These backslashes

will break the line.

\begin{itemize}
  \item First bullet point.
  \item Second one.
\end{itemize}

• First bullet point.
• Second one.

Sections

It’s often important to give a logical structure to your document, especially when writing a paper. You can split up your article in different sections and subsections²:

\section{This is the section title}
\subsection{These titles will be printed in your document}
\subsubsection{These will also show up in your table of content}

Putting All Together

Congrats! You’ve just learned the basics of $\LaTeX$! Now, putting all together, your document code may look something like this:

\documentclass{article} % Specifies that we're writing an article
\usepackage{amsmath} % Imports amsmath
\title{My First \LaTeX{} Article} % Defines the title
\author{John Doe}
\date{January 1st, 2000}
\begin{document} % Begins the document environment
  \maketitle % Prints the title
  \newpage % Ensures that the article starts from the next page
  \section{My First Section}
  Hello, world! I'm finally writing my first document. I've learned that \textbf{this is how you make a text bold}.
  % This is a comment, hidden in the final output
  \section{A Section for a Very Important Equation}
  This is an equation:
  \begin{equation} % Begins an equation environment
    E_0 = mc^2
  \end{equation}
\end{document}

Tip

You’ve just scratched the surface. For more formatting options, you can check out this great guide.

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