Either  —adj. & pron. 1 one or the other of two (either of you can go; you may have either book). 2 each of two (houses on either side of the road). —adv. & conj. 1 as one possibility (is either right or wrong). 2 as one choice or alternative; which way you will (either come in or go out). 3 (with neg.) A any more than the other (if you do not go, i shall not either). B moreover (there is no time to lose, either). [old english]