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7.1 \label



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:


for chapters


for lower-level sectioning commands


for figures


for tables


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}
This is Section~\ref{sec:test}.
  \caption{caption text}
See Figure~\ref{fig:test}.

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