Labels and cross-references

Never write "see Section 3" by hand

• If you write a number by hand and later add a section, every number is wrong.
• LaTeX solves this with labels. Tag something:

\section{Methods}\label{sec:methods}

• The name sec:methods is just a nickname you choose.

Refer to it anywhere

• Then point at it with \ref — LaTeX inserts the current number:

As shown in Section~\ref{sec:methods}, ...

• The ~ is a space that never breaks across lines, so "Section" and its number stay together.

It needs two passes

• On the first compile LaTeX learns the numbers; on the second it fills them in.
• Our Run does this for you automatically. (The same trick powers a table of contents.)