one or the other of two: You may sit at either end of the table.
each of two; the one and the other: There are trees on either side of the river.
one or the other: There are two roads into the town, and you can take either. Either will do.
(a coordinating conjunction that, when preceding a word or statement followed by the disjunctive or, serves to emphasize the possibility of choice): Either come or write.
also; too; as well; to the same degree (used after negative clauses coordinated by and, or, or nor, or after negative subordinate clauses): He's not fond of parties, and I'm not either. If you don't come, she won't come either.