A topological space XX satisfies the T DT_D separation axiom if, given any element aa of XX, the singleton subset {a}\{a\} is an open subspace in the induced topology on its own closure. In other words, for every point aa, there is a neighbourhood UU of aa such that the intersection of UU and Cl{a}Cl\{a\} is {a}\{a\}.

Created on July 1, 2010 at 17:33:55. See the history of this page for a list of all contributions to it.