KnowraUrysohn's lemmaLinked fromLinked fromThe 6 pages that link to Urysohn's lemma, each with the reason it gives.All 6Related 6Normal spaceRelated: It converts normality directly into a continuous numerical distinction between closed sets.Felix HausdorffRelated: It illustrates how stronger separation conditions yield continuous functions.Separation axiomRelated: It translates normality into separation by a continuous numerical function.Tietze extension theoremRelated: It supplies the separating functions used to construct extensions of bounded functions.Urysohn's metrization theoremRelated: It provides the continuous functions used to distinguish points from closed sets.Nagata–Smirnov metrization theoremRelated: Separation by continuous functions is a standard route from topological structure toward metric constructions.