adverb
1
BAD : I shall either go home to Brazil or my family will come to England.
GOOD : Either I shall go home to Brazil or my family will come to England.
BAD : We either can go by bus or by car.
GOOD : We can go either by bus or by car.
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The position of either should be the same as the position of or (i.e. immediately before a subject, immediately before a main verb, immediately after a verb, etc): 'Either stay or go.' 'You should either stay or go.' 'You should stay either here or at home.' 'You should stay with either me or your uncle.'
Note that this rule applies mainly in formal styles. In everyday conversation, either often goes immediately before the main verb: 'We can either go by bus or by car.'
2
BAD : In fact, a motorway wouldn't either disturb the animals because they are used to cars.
GOOD : In fact, a motorway wouldn't disturb the animals either because they are used to cars.
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When either is used after not/never etc, it goes at the end of the clause: 'John isn't going to the party, and Ray doesn't want to go either.'