*Definition [#b82be9cc]
-Let x be a point of a topological space (X,τ). The set of all y for which is not [[weakly separated]] from x is called  the kernel of x.


*Reference [#z64031be]
-Aull, Charles E.; Thron, W.J., ''Separation axioms between T0 and T1.'', (English) [J] Nederl. Akad. Wet., Proc., Ser. A 65, 26-37 (1962).