\begin{definition}[Definition:Closure (Topology)/Definition 5]
Let $T = \struct {S, \tau}$ be a topological space.
Let $H \subseteq S$.
The '''closure of $H$ (in $T$)''' is the union of the set of all isolated points of $H$ and the set of all limit points of $H$:
:$H^- := H^i \cup H'$
\end{definition}