Etimology
From Middle English either, from Old English ǣġhwæþer, from *aiwon + *gahwaþera. Akin to Old Saxon eogihwethar, iahwethar (Low German jeed); Old Dutch *iogewether, *iowether, *iother (Dutch ieder); Old High German eogihwedar, iegihweder, ieweder (German jeder).
determiner
either
Any one (of two).
Each of two; both. [from 9th c.]
(now rare) Any one (of more than two).
Examples
You can have it in either colour.
There is a locomotive at either end of the train, one pulling and the other pushing.
His flowing hair In curls on either cheek played.
Her hands, long and beautiful, lay on either side of her face.
I hope you will be ready to own publicly, whenever you shall be called to it, that by your great and frequent urgency you prevailed on me to publish a very loose and uncorrect account of my travels, with directions to hire some young gentleman of either university to put them in order, and correct the style, as my cousin Dampier did, by my advice, in his book called “A Voyage round the world.”
They entreat, they pray, they beg, they supplicate that you will make no scruple to go to your uncle Antony's […] .
Related words
synonyms
(each of two): both, each
pronoun
either
One or the other of two people or things.
(obsolete) Both, each of two or more.
Examples
He made me two offers, but I did not accept either.
Hodgson may now have to bring in James Milner on the left and, on that basis, a certain amount of gloss was taken off a night on which Welbeck scored twice but barely celebrated either before leaving the pitch angrily complaining to the Slovakian referee.
Scarce a palm of ground could be gotten by either of the three.
And either vowd with all their power and wit, / To let not others honour be defaste […]
There have been three famous talkers in Great British, either of whom would illustrate what I say about dogmatists.
adverb
either (not comparable)
(conjunctive, after a negative) As well.
Examples
I don't like him, and I don't like her either.
I know a cheap Spanish restaurant. It's not far from here, either.
But Richmond […] appeared to lose himself in his own reflections. Some pickled crab, which he had not touched, had been removed with a damson pie; and his sister saw […] that he had eaten no more than a spoonful of that either.
conjunction
either
Introduces the first of two (or occasionally more) options or possibilities, the second (or last) of which is introduced by “or”.
Examples
Either you eat your dinner or you go to your room.
You can have either potatoes or rice with that, but not both.
You'll be either early, late, or on time.
You can't be a table and a chair. You're either a Jew or a gentile.
Thus, when he drew up instructions in lawyer language […] his clerks […] understood him very well. If he had written a love letter, or a farce, or a ballade, or a story, no one, either clerks, or friends, or compositors, would have understood anything but a word here and a word there.