I. ˈē-thər also ˈī- adjective
Etymology: Middle English, from Old English ǣghwæther both, each, from ā always + ge-, collective prefix + hwæther which of two, whether — more at aye , co-
Date: before 12th century
1. : being the one and the other of two : each
flowers blooming on either side of the walk
plays either instrument well
2. : being the one or the other of two
take either road
II. pronoun
Date: before 12th century
: the one or the other
take either of the two routes
III. conjunction
Date: before 12th century
— used as a function word before two or more coordinate words, phrases, or clauses joined usually by or to indicate that what immediately follows is the first of two or more alternatives
can be used either as a guest room or as an office
IV. adverb
Date: 15th century
1. : likewise , moreover — used for emphasis after a negative
not smart or handsome either
2. : for that matter — used for emphasis after an alternative following a question or conditional clause especially where negation is implied
who answers for the Irish parliament? or army either ? — Robert Browning