\label (LaTeX2e unofficial reference manual (November 2018))

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### 7.1 `\label`

Synopsis:

    \label{key}

Assign a reference number to key. In ordinary text `\label{key}` assigns to key the number of the current sectional unit. Inside an environment with numbering, such as a `table` or `theorem` environment, `\label{key}` assigns to key the number of that environment. Retrieve the assigned number with the `\ref{key}` command (see \ref).

A key name can consist of any sequence of letters, digits, or common punctuation characters. Upper and lowercase letters are distinguished, as usual.

A common convention is to use labels consisting of a prefix and a suffix separated by a colon or period. Thus, `\label{fig:Post}` is a label for a figure with a portrait of Emil Post. This helps to avoid accidentally creating two labels with the same name, and makes your source more readable. Some commonly-used prefixes:

`ch`

  for chapters

`sec`
`subsec`

  for lower-level sectioning commands

`fig`

  for figures

`tab`

  for tables

`eq`

  for equations

In the auxiliary file the reference information is kept as the text of a command of the form `\newlabel{label}{{currentlabel}{pagenumber}}`. Here currentlabel is the current value of the macro `\@currentlabel` that is usually updated whenever you call `\refstepcounter{counter}`.

Below, the key `sec:test` will get the number of the current section and the key `fig:test` will get the number of the figure. (Incidentally, put labels after captions in figures and tables.)

    \section{section name}
    \label{sec:test}
    This is Section~\ref{sec:test}.
    \begin{figure}
      ...
      \caption{caption text}
      \label{fig:test}
    \end{figure}
    See Figure~\ref{fig:test}.

Unofficial LaTeX2e reference manual