Either is about one or the other of two people or things. It can also mean one and the other of two people or things. As for neither, it’s not one or the other of two people or things. As determiners, either and neither come before a singular countable noun.A noun that follows either or neither is singular.
- You can choose either piece, and I will take the other one.
- He was punched hard on the nose, but neither nostril was bleeding.
Either: one or the other of two.
- I don’t mind which fish. Just give me either one, please.
- You can take either road; both roads will lead you there.
- You may use either hand to hold it.
Either: one and the other of two.
- It has big ears on either side (= both sides) of its head.
- There are toilets at either end of the long corridor.
- She will return home to live if either of the parents dies.
Either is commonly used before a pronoun.
- Either she is telling the truth, or she does not know she is telling a lie.
- Either he or his brother is going to fetch the mother home.
Neither is used to show not either of two people or things.
- Neither one of our parents is a smother.
- Neither sweater you bought for me fits me.
- Neither coin he found is foreign.