*Definition [#rf171ffd]
-A topological space (X,τ) is called pre-T_0 iff to each pair of distinct points x, y in X, there exists a [[pre-open]] set containing one of the points but not the other.

*Reference [#q0ee3267]
-Athisaya Ponmani, S.; Lellis Thivagar, M., ''Another form of separation axioms.'' ,  (English) [J] Methods Funct. Anal. Topol. 13, No. 4, 380-385 (2007).