New classes of sets called Ω-closed sets and Ωs-closed sets are introduced and studied. Also, we introduce and study Ω-continuous functions and Ωs-continuous functions and prove pasting lemma for these functions. Moreover, we introduce classes of topological spaces called Ω-T_1/2 and Ω-T_s.

@ 2005 Akade´miai Kiado´, Budapest.