Definition:Circular Relation

Definition
Let $\mathcal R \subseteq S \times S$ be a relation in $S$.

$\mathcal R$ is circular iff:
 * $\left({x, y}\right) \in \mathcal R \land \left({y,z}\right) \in \mathcal{R} \implies \left({z, x}\right) \in \mathcal R$