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Normal space
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<p>In <a href="/facts/Topology/2EqW47cU">topology</a> and related branches of <a href="/facts/Mathematics/pxTouaz4">mathematics</a>, a normal space is a <a href="/facts/Topological_space/v2ut7CbK">topological space</a> <i>X</i> that satisfies Axiom T4: every two disjoint <a href="/facts/Closed_set/upYnRTUj">closed sets</a> of <i>X</i> have disjoint <a href="/facts/Open_neighborhood/XHKgrpkp">open neighborhoods</a>. A normal <a href="/facts/Hausdorff_space/gbKIrusl">Hausdorff space</a> is also called a T4 space. These conditions are examples of <a href="/facts/Separation_axiom/s4CKf8gp">separation axioms</a> and their further strengthenings define completely normal Hausdorff spaces, or T5 spaces, and perfectly normal Hausdorff spaces, or T6 spaces. </p>