*Definition [#hacfe22f]
-A topological space (X, τ) is called λ-T_{1/2} if every singleton is [[λ-open]] or [[λ-closed]].

*Reference [#ub9862ca]
-Caldas Miguel, Jafari Saeid, ''On some low separation axioms via λ-open and λ-closure operator.'',  Rend. Circ. Mat. Palermo (2) 54 (2005), no. 2, 195–208.