How do you spell Either

Available Definitions:
1)  a. & pron. - One of two; the one or the other; -- properly used of two things, but sometimes of a larger number, for any one.
2)  a. & pron. - Each of two; the one and the other; both; -- formerly, also, each of any number.
3)  conj. Either - precedes two, or more, coordinate words or phrases, and is introductory to an alternative. It is correlative to or.