#
nLab

restriction

Contents
# Contents

## Definition

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 16, 2018 at 08:37:26.
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