Definition:Regular Closed Set

Definition
Let $T$ be a topological space.

Let $A \subseteq T$.

Then $A$ is regular closed in $T$ :
 * $A = A^{\circ -}$

That is, $A$ equals the closure of its interior.

Also known as
Some sources use the term regularly closed, but this is not used on.

Also see

 * Definition:Regular Open Set