either用作代词时,意为“二者之一”,可单独使用,也可以和表示范围的of短语连用,of后的名词一般为复数,并且是特指.例如：
—Do you want tea or coffee?你要茶还是咖啡?
—Either is OK.哪一种都行.
Is either of your parents coming to see you next week?下周你父亲或母亲要来看你吗?
注：either作主语时,谓语动词应用单数形式,of后面的名词在数上应是“两个”,并带有限定词,如往往说either of the／your boxes,而不说either of boxes.
二、either用作形容词时,可修饰单数可数名词,意为“两个中任一个”,其谓语动词也应用单数形式.例如：
Come on Saturday or Sunday.Either day is OK.星期六或星期天来吧,这两天哪天都行.
There are lots of shops on either side of the street.（＝There are lots of shops on both sides of the street.）街道两边有许多商店.
三、either用作副词时,意为“也（不）”,用于否定句的句末.例如：
If you don't go there,I won't,either.如果你不去那里,我也不去.
四、either...or...可用来连接两个词类相同的词,意为“或者……或者……”、“要么……要么……”.例如：
You may hand in your exercise book either before class or after class.你可以在课前或课后交练习本.
注意：either...or...连接两个主语时,其谓语应与后面的主语在人称或数上保持一致.如：Either you or he is wrong.要么你错了,要么他错了.
Either you or I am going there.要么你去那里,要么我去那里.