\begin{definition}[Definition:Hereditary Property (Topology)]
Let $\xi$ be a property whose domain is the set of all topological spaces.
Then $\xi$ is a '''hereditary property''' {{iff}}:
:$\map \xi X \implies \map \xi Y$
where $Y$ is a subspace of $X$.
That is, whenever a topological space has $\xi$, then so does any subspace.
\end{definition}