Solution (source code)

= Solution

A <topology> on $X$ is a family $\mathcal T$ of subsets containing $\varnothing$ and $X$, closed under arbitrary unions and finite intersections. Its members are the <open sets>. A <Hausdorff space> separates each pair of distinct points by disjoint open neighbourhoods; a <compact space> is one for which every <open cover> has a finite subcover.