*Definition [#o6a2804f]
A subset S of a topological space is called b-open iff &ref(http://www.eaflux.com/imgtex/imgtex.fcgi?%5bres=100%5d%7b$S%5csubset%5cmathrm%7bcl%7d%28%5cmathrm%7bint%7d%28S%29%29%5ccup%5cmathrm%7bint%7d%28%5cmathrm%7bcl%7d%28S%29%29$%7d%25.png);.
*Property [#ob2dbdc6]
-Every [[semiopen]] set is b-open.
-Every [[preopen]] set is b-open.
-Every b-open set is [[semipreopen]].
*Reference [#u230cb25]
M. Caldas, S. Jafari and R. M. Latif, Applications of b-open sets and (b,s)-continuous functions'', Technical Report of Department of Mathematical Sciences of King Fahd University of Petroleum and Minerals  TR400 (July 2008).