# Contents

## Definition

A (binary) relation $\sim$ on a set $A$ is reflexive if every element of $A$ is related to itself:

$\forall (x: A),\; x \sim x$

In the language of the $2$-poset Rel of sets and relations, a relation $R: A \to A$ is reflexive if it contains the identity relation on $A$:

$\id_A \subseteq R$

Revised on December 2, 2012 20:17:53 by Urs Schreiber (82.113.106.154)