There is a locomotive at either end of the train, one pulling and the other pushing.
There are roses on either side of the garden.
(often proscribed) Any one (of more than two).
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.”
pronoun
One or the other of two people or things.
He made me two offers, but I did not accept either.
(obsolete) Both, each of two or more.
adverb
(conjunctive, after a negative) As well.
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.
conjunction
Introduces the first of two (or occasionally more) options or possibilities, the second (or last) of which is introduced by “or”.
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.
Either you'll finish your homework or you'll be grounded you home.