Definition:Univalent Relation

Definition
Let $\RR$ be a relation on a set $S$.

Then $\RR$ is univalent :


 * $\RR \circ \RR^{-1} \subseteq \Delta_S$

That is, $\RR$ composed with its inverse $\RR^{-1}$ is a subset of the diagonal relation on $S$.