英语中either既可以做代词表示两者之中的任何一个，也可以做副词，意思是也，用于否定句，往往放在句子的末尾，用逗号隔开。
例如
Either of the two students is reading in the room.
I don't like English ，either.
英语中too是可以做副词，意思是也，放在句子的末尾，逗号隔开，用于肯定句。too也可以做副词，意思是太，修饰其他的形容词或者副词。
例如
The subject is too difficult for me to study
I like English ，too.
英语当中both可以做代词，意思是两者都。
Both of the students are reading in the library.
Both the teacher and the boy are ready in the library.
