\begin{definition}[Definition:Exterior (Topology)/Notation]
Let $T$ be a topological space.
Let $H \subseteq T$.
The exterior of $H$ can be denoted:
:$\map {\mathrm {Ext} } H$
:$H^e$
The first is regarded by some as cumbersome, but has the advantage of being clear.
$H^e$ is neat and compact, but has the disadvantage of being relatively obscure.
On {{ProofWiki}}, the notation of choice is $H^e$.
Category:Definitions/Set Exteriors
\end{definition}