For any two points , there is an open set such that and or and . A space fulfilling this axiom is called a T0-space.
See alsoSeparation Axioms, T0-Space
This entry contributed by Margherita Barile
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Barile, Margherita. "T_0-Separation Axiom." From MathWorld--A Wolfram Web Resource, created by Eric W. Weisstein. https://mathworld.wolfram.com/T0-SeparationAxiom.html