- either [ē′thər, ī′thər]adj.[ME < OE æghwæther < a (æ), always (see AY) + gehwæther, each of two (see WHETHER): akin to, and of same formation as, OHG eogihwedar]1. one or the other (of two) [use either hand]2. each (of two); the one and the other [he had a tool in either hand]pron.one or the other (of two)conj.the first element of the pair of disjunctive correlatives either … or, implying a choice of alternatives [either go or stay ]: either … or is sometimes used to refer to more than two, although this use is objected to by some [bring either cookies, doughnuts, or some other kind of pastry]adv.1. any more than the other; also: used after negative expressions [if you don't go, I won't either]2. Informal certainly; indeed: used as an intensifier in a negative statement [“It's mine.” “It isn't either!”]
English World dictionary. V. Neufeldt. 2014.