semi-decidable

Of a set, such that there is a deterministic algorithm such that if an element is a…Of a set, such that there is a deterministic algorithm such that (a) if an element is a member of the set, the algorithm halts with the result "positive", and (b) if an element is not a member of the set, (i) the algorithm does not halt, or (ii) if it does, then with the result "negative".