In this paper we prove that each subspace of an Alexandroff T 0-space is semi-T 1 2. In particular, any subspace of the folder X n , where n is a positive integer and X is either the Khalimsky line (Z, τ K), the Marcus-Wyse plane (Z 2 , τ MW) or any partially ordered set with the upper topology is semi-T 1 2. Then we study the basic properties of spaces possessing the axiom semi-T 1 2 such as finite productiveness and monotonicity.

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