C_D

Definition

• A topological space (X,τ) is said to be C_D if for every x∈X, either {x}' is empty or {x}' is not closed.

Property

• C_D + T_D = T_1.

Reference

• Guia, Josep, Essentially T_D and essentially T_UD spaces., Bull. Math. Soc. Sci. Math. R. S. Roumanie (N.S.) 32(80) (1988), no. 3, 227-233.