#
nLab

restriction

# Contents

## Definiion

The **restriction** of a function $f: X \to Y$ to a subset $U$ of $X$ is simply the composite of $f$ and the inclusion function of $U$:

$U \stackrel{i_U}\to X \stackrel{f}\to Y .$

It is often written as $f_{|U}: U \to Y$, or a variation on that theme.

Last revised on November 14, 2017 at 06:49:31.
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