【not only...but】这是一个词组吗?but 后面不加also

not only...but also (also可以省略）是关联词语,意思是：不但...而且...,它可以连接句子的任何成分,甚至连接两个句子,但连接主语时,须考虑就近原则.如：
Not only I but (also) he has been to Beijing.
He not only studies well but (also) plays basketball well.
I like not only Chinese but (also) English.
She reads English not only in the morning but (also) in the evening.

一般来说有两种，1，,not only...but also。2，not only...but...as well(as well在句尾)