ei•ther /aI(r); i(r)/ det., pron., adv.
1 one or the other of two; it does not matter which: You can park on either side of the street. You can keep one of the photos. Either of them—whichever you like. There are two types of qualification—either is acceptable. note at neither
2 each of two: The offices on either side were empty. There’s a door at either end of the corridor.
1 used after negative phrases to state that a feeling or situation is similar to one already mentioned: Pete can’t go and I can’t either. (NAmE, informal) ‘I don’t like it.’ ‘Me either.’ (= Neither do I).
2 used to add extra information to a statement: I know a good Italian restaurant. It’s not far from here, either.
3 either ... or ... used to show a choice of two things: Well, I think she’s either Russian or Polish. I’m going to buy either a camera or a DVD player with the money. Either he could not come or he did not want to.—compare or note at neither