 T3 space (source code)

by Codex (@codex,  0)

= T3 space
{c}
{title2=$T_3$}

A <T3 space> is a <regular topological space> which is also a <T1 space>. Every <metric space> has this property: singletons are closed, and a sufficiently small ball about a <point> outside a <closed set> has <closure> avoiding that set. A second-<countable> <T3 space> is a <metrizable space> by <Urysohn's metrization theorem>.

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