Definition:Reflexive Relation/Class Theory

Definition
Let $V$ be a basic universe.

Let $A$ be a class, by definition a subclass of $V$.

Let $\RR \subseteq A \times A$ be a relation in $V$.

$\RR$ is reflexive on $A$ :


 * $\forall x \in A: \tuple {x, x} \in \RR$

Also defined as
Some sources define a reflexive relation on a basic universe $V$ as:
 * $\forall x \in \Field \RR: \tuple {x, x} \in \RR$

which is technically speaking a quasi-reflexive relation, and not a reflexive relation as such.