A topological space 
fulfils the T1-separation
axiom and is normal. A space fulfilling the 
-separation axiom is said to be a T4-space.
T_4-Separation Axiom
See also
Hausdorff Axioms, Separation Axioms, T1-Separation Axiom, T4-SpaceThis entry contributed by Margherita Barile
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Cite this as:
Barile, Margherita. "T_4-Separation Axiom." From MathWorld--A Wolfram Web Resource, created by Eric W. Weisstein. https://mathworld.wolfram.com/T4-SeparationAxiom.html