(·adj & ·pron) each of two; the one and the other; both;
formerly, also, each of any number.
2. either (·adj & ·pron) one of two; the one or the other;
properly used of two things, but sometimes of a larger number, for any one.
3. either (·conj either) precedes two, or more, coordinate words or phrases, and is introductory to an alternative. it is correlative to or.