either
1.either在用作代词或形容词的时候指“两个中间的任何一个”，如Either of the two will do和You may put the chair on either side of the table。有时也指“两个以上的中间的任何一个”。如Either of the three will do和You may put the ring on either finger of your hand。但这种用法不算正当，该避免，通常该用any或any one。
2.either有时指“两个中间的每一个”（each of the two），如I have two typewriters, but either is out of order now和There is a chair on either side of the table。但这种用法现在不很普通，最好避免，通常该用each。注意这种用法跟1里所讲的不同，There is a chair on either side of the table里的either side等于each side，但You may put the chair on either side of the table里的either side并不等于each side。You may put a chair on either side of the table可能有两个不同的意思：“你可以放一把椅子在这桌子的任何一边（只放一把椅子）。”或“你可以放一把椅子在这桌子的每一边（共放两把椅子）。”这句不明白，该改作You may put a chair on either one or the other side of the table或You may put a chair on each side of the table。
比较下面两句：
Two of her brothers sat on either side of her. （1.在她的每一边坐着她的弟兄们中间的两个［有四个弟兄坐着］。2.在她的两边坐着她的弟兄们中间的两个［有两个弟兄坐着］。）
Her two brothers sat on either side of her. （她的两个弟兄坐在她的两边。）
第一句不明白，该改作There were two of her brothers sitting on each side of her或There was one of her brothers sitting on each side of her。第二句也不妥当，该改作There was one of her two brothers sitting on each side of her或One of her two brothers sat on one side of her, and the other sat on the other side。第一句假使改作Two of her brothers sat on each side of her和One of her brothers sat on each side of her也不妥当，因为好像说一个人同时可以坐在另一个人的两边。
3.either（代词或形容词）属于单数形式，如Either is good和Either book is good。把它当作复数是英美人常有的错误。
4.either...or...所连接的主语的动词跟后一个名词或代词相一致。例如：
- Either he or you are wrong.
- Either you or he is worng.
- Either the father or the sons are wrong.
- Either the sons or the father is wrong.
但这种结构往往被避免用，如上面四句可以改作：
- Either he is wrong, or you are.
- Either you are wrong, or he is.
- Either the father is wrong, or the sons are.
- Either the sons are wrong, or the father is.
5.在1里讲过，把代词或形容词either用来指“两个以上的中间的任何一个”是不正当的。但把either（副词或连接词）...or...用于两个以上是正当的，如Either you, (or) your brother, or your sister will do和You may write the application either in Chinese, (or) in Russian, (or) in English, or in French。
6.用either...or...比单用or语气重些。例如：
- I do not want tea or coffee.
I do not want either tea or coffee. - You may take tea or coffee.
You may take either tea or coffee. - If you want tea or coffee, I will give you some.
If you want either tea or coffee, I will give you some.
比较下面两句：
- Do you want tea or coffee? （1.你要茶，还是要咖啡？［你要哪一种？］2.你要茶或咖啡么？）
- Do you want either tea or coffee? （你要茶或咖啡么？）
7.either...or...跟both...and...受同样的规则的限制，如可以说either boys or girls，也可以说either with boys or with girls和with either boys or girls，但最好不说either with boys or girls。参见both 4
8.注意下面各句里的either作副词用：
- If you do not go to see him, I shall not either.
- You will not go to see him, and I shall not either.
- I do not want this, or that, or the third one either.
- He is not clever or handsome either.
- John, or Henry either, might have done it.
