Definition
- A subset A of a topological space (X,τ) is called δ-open if , where is the δ-interior of the set A.
Reference
- Caldas, M.; Ganster, M.; Georgiou, D. N.; Jafari, S.; Moshokoa, S. P., δ-semiopen sets in topology. (English summary), Proceedings of the 19th Summer Conference on Topology and its Applications., Topology Proc. 29 (2005), no. 2, 369–383.