英語中either既可以做代詞表示兩者之中的任何一個，也可以做副詞，意思是也，用於否定句，往往放在句子的末尾，用逗號隔開。
例如
Either of the two students is reading in the room.
I don't like English ，either.
英語中too是可以做副詞，意思是也，放在句子的末尾，逗號隔開，用於肯定句。too也可以做副詞，意思是太，修飾其他的形容詞或者副詞。
例如
The subject is too difficult for me to study
I like English ，too.
英語當中both可以做代詞，意思是兩者都。
Both of the students are reading in the library.
Both the teacher and the boy are ready in the library.
