*Definition [#a2f5c671]
-A topological space (X, τ) is called a semi-T_0 space if for x, y ∈ X such that &ref(http://www.eaflux.com/imgtex/imgtex.fcgi?%5bres=100%5d%7b%5c%5b%20x%5cneq%20y%20%5c%5d%7d%25.png); there exists a [[semi-open set>semi-open]] containing x but not y or a [[semi-open set>semi-open]] containing y but not x.

*Reference [#ve3ae3c3]
-Bhattacharyya Paritosh, Lahiri B. K., ''Semigeneralized closed sets in topology.'', Indian J. Math. 29 (1987), no. 3, 375-382 (1988).