Definition:Reflexive Transitive Closure/Reflexive Closure of Transitive Closure

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


 * $\mathcal R^* = \left({\mathcal R^+}\right)^=$