Basic Syntax I

Because LaTeX is a markup language, the majority of your file will simply be regular text. Therefore, something is needed to tell the computer when a piece of text is actually a command. For this, we always use the backslash: \.

Arguments

Commands require arguments, which can be required or optional. These can be mixed. A command can have some required and some optional arguments, or only optional ones, or only required ones. And in some rare cases, no arguments at all.

Required Arguments

For example, when emphasizing a piece of text, we need to supply which piece of text we want emphasized. It’s required. If we leave it out, it emphasizes nothing. Some commands go even further, and throw errors when you don’t supply the required arguments.

Required arguments are placed between braces:

1\command{argument1}{argument2}{…}

1This text is \textit{written in italics}

Optional Arguments

For example, if we want to insert a new line, we could supply how much white space we want between this new line and the previous one. But, if we leave it out, everything’s fine, and it just takes the standard line height.

Optional arguments are placed between brackets, and separated by commas if there are multiple:

1\command[argument1, argument2, …]

1This is a\\regular line break.
2
3This is a\\[20mm] longer line break

Combined Arguments

When a command has both optional and required arguments, you always need to provide the optional ones first.

1\begin{thebibliography}{2}
2     \bibitem[SomeText]{book1} Book 1, written by Someone, in 1900
3     \bibitem{book2} Book 2, written by Someone Else, in 1950
4\end{thebibliography}

Nesting Commands

You can nest commands as much as you like. In general, though, it’s recommended to keep the number of levels in markup languages to a minimum. In the same way that adding a fourth or fifth subheading to a webpage usually means that you’re trying to do too much.

Try to never go further than three levels deep.