Definition:Restriction/Relation/Class Theory

Definition
Let $V$ be a basic universe.

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

Let $A \subseteq V$ be a class.

The restriction of $\RR$ to $A$ is the relation on $A \times A$ defined as:


 * $\RR {\restriction_A}: = \RR \cap \paren {A \times A}$

Note that the parenthesis is not necessary in the above, but it does make the meaning clearer.