这几个词与数字有关。
一，either neither both与数字“2”有关。因此，要谈论两个的时候，才能用这三个词。
either 两个中任何一个，是单数。
neither 两个中一个也没有，是单数。
both 两个中的两个，是复数。
My parents are teachers. Either of them teaches English.我的父母是老师。两位都教英语。
Both of the twins like playing basketball, but neither of them enjoys music.这对双胞胎都喜欢打篮球，但是他们两位都不喜欢音乐。
二，all none each 与数字“3”有关。
all 大于等于3个中，所有的，复数。
each 大于等于2个中，每一个，是单数。
none 大于等于3个中，一个也没有。单数，复数都行。
There are many students on the playground, and all of them come from the countryside.操场上有很多学生，他们都是来自农村。
I have a lot of friends, but none of them can help you.我有很多朋友，但是，他们一个也帮不了你。
Each of the two students has a book. 这两个学生都有一本书。
There are many books in the shop. Each costs ten yuan.书店里有很多书，每本十元。
I have lots of pens, but none of them are（is）good.我有很多钢笔，但是没有一支是好的。
选词填空（either neither both all none each ）
The man bought some books, but_of them was good.
Would you like to come on Monday or Tuesday?
_will do. I'm free all the time.
_of the couple teaches us English. They are great.
In order to win the game, the students are practicing day after day, and _of them would lose.
There are beautiful flowers on _side of the street.Let's take some pictures.（either both all neither none）