(a) As an affirmative reply to a direct or an indirect question: yes; seien ~; (b) as an affirmation of the truth or correctness of an assertion, a proposition, etc.: that is right, it is so, yes; (c) as an indication of agreement, assent, or acquiescence to a demand, request, an invitation to act, imposed condition, etc.: that is agreed, so be it, yes; (d) as a contradiction of the answer to a question: on the contrary, yes; also, with partial or qualified agreement to a statement: ~ ac (but), yes, but; (e) as an introductory word of response, often indicating mere emphasis, sometimes scorn, etc.: yes, indeed; also, implying impatience: yes, yes; also, implying skepticism: well, yes.

In selected verb phrases: (a) seien ~ or nai (nai or ~), to make a reply one way or the other; seien nouther ~ ne nai (nai ne ~), ne answeren nai ne ~, etc., make no reply, say nothing at all; (b) affermen other ~ or nai, seien or ~ or nai, to assert one thing or the contrary; seien ~…seien (not) nai, etc., state an opinion or its contradiction; assert one or the other side in an argument;—used of a pair of speakers; (c) bihoten (sweren) ~, to promise (swear) that something is so or will happen; (d) seien ~ and nai (~ ~ and nai nai), sweren ~ ~ nai nai, to utter a mild affirmation or denial; seien ~ or nai, give consent or refusal.