*Definition [#occ476f6]
A subset S of a topological space X is called semi-regular (or regular semi-open) if there is some [[regular open]] set V such that &ref(http://www.eaflux.com/imgtex/imgtex.fcgi?%5bres=100%5d%7b$V%5csubset%20S%5csubset%5cmathrm%7bcl%7dV$%7d%25.png);.
*Reference [#m75e4d2c]
J. Dontchev and M. Ganster, ''Some comments on θ-irresolute and quasi-irresolute functions'', Serdica Math. J. 21 (1995), 67-74