Definition:Closure (Topology)/Definition 6

Definition
Let $T = \left({S, \tau}\right)$ be a topological space.

Let $H \subseteq S$.

The closure of $H$ (in $T$), denoted $H^-$, is the set of all adherent points of $H$.

Adherent Point
Let $A \subseteq S$.

Also see

 * Equivalence of Definitions of Topological Closure