*Definition [#d94262dd]
-For a subset A of X, the union of all [[β-open]] sets of X contained in A is called the β-interior (in short β-int(A)) of A.

*Reference [#hacca97b]
-Basu, C. K.; Afsan, B. M. Uzzal; Ghosh, M. K., ''A class of functions and separation axioms with respect to an operation.'' (English summary), Hacet. J. Math. Stat. 38 (2009), no. 2, 103-118.