Definition
Let A be a subset of a topological space X.
By
we denote the set
(see semi-θ-closed).
A is called
-set if
.
A is called (Λ,sθ)-closed (or
-semi-θ-closed) if A=T∩C for some
-set T and some semi-θ-closed set C.
The complement of a (Λ,sθ)-closed set is called (Λ,sθ)-open (or
-semi-θ-open).
Reference
M. Caldas, M. Ganster, D. N. Georgiou, S. Jafari, V. Popa, On a Generalization of Closed Sets, Kyungpook Math. J. 47(2007), 155-164.