Definition:Reflexive Transitive Closure/Reflexive Closure of Transitive Closure

Definition
Let $\RR$ be a relation on a set $S$. The reflexive transitive closure of $\RR$ is denoted $\RR^*$, and is defined as the reflexive closure of the transitive closure of $\RR$:


 * $\mathcal R^* = \paren {\RR^+}^=$