由一个主句和一个或一个以上从句构成的句子叫做复合句。所谓主句，就是在复合句中起统领作用的句子，它是全句的主体，通常可以独立存在；而从句则是复合句的一个句子成分，不能独立存在。

如：

You’ll feel better after you take the pills. 吃完药丸后你会感到好一些。

The police learned that he wasn’t there at that time. 警察获知他那时不在场。

这两句都是复合句，第一句的主句是You’ll feel better，从句是after you take the pills，由after引导，在整个复合句中用作状语，表示时间；

第二句的主句是The police learned是主句，that he wasn’t there at that time是从句，由that引导，在整个复合句中用作宾语。

注意，英语的复合句不是简单句的反面，不要将它误解为“复杂句”。事实上，英语的简单句有时也可以比较“复杂”，而复合句也可以比较“简单”。

如：

He stopped because he was tired. 他停下来是因为他累了。

这个句子比较“简单”，却是一个典型的复合句，其中的he stopped是主句，because he was tired是从句，在复合句中用作状语，表示原因。

从句在复合句用作主语，我们就叫它为主语从句；从句在复合句用作宾语，我们就叫它为宾语从句；从句在复合句用作状语，我们就叫它为状语从句；等等。

如：

He answered that he knew nothing about it. 他回答说他不知情。

The trouble is that I have lost his address. 麻烦的是我把他的地址丢了。

He was rather pleased when he won that prize. 他获奖后相当高兴。

She was not in the train that arrived just now. 她不在刚到的那列车上。

六种英语复合句是

1.主语从句

That he finished the work in such a short time surprised us.

2.宾语从句

I hear that he will be back in a week.

3.表语从句

This is why he is late for the meeting.

4.同位语从句

I heard the news that our team won the match.

5.定语从句

This is the book that he gave me yesterday.

6.状语从句

He was absent from school bacause he was ill.