\begin{definition}[Definition:Interior Point (Topology)/Definition 2]
Let $T = \struct {S, \tau}$ be a topological space.
Let $H \subseteq S$.
Let $h \in H$.
$h$ is an '''interior point''' of $H$ {{iff}} $h$ has an open neighborhood $N_h$ such that $N_h \subseteq H$.
\end{definition}