凡带有从属分句（简称“从句”）作为分句成分的句子，便是复杂句（complex sentence）。这种从属分句可以是名词性分句，也可以是状语分句。

1．    带名词性分句的复杂句

名词性分句能在句中起名词词组的作用，可作句子的主语（主语从句）、宾语（宾语从句）、补语（补语从句），能引导名词性分句的词语有that， who， which， what， when， why， how，where， whether（or）， if等。

A）  主语从句 (subject clause)

What he said is not true.

Who damaged the computer is yet unknown.

How the thief managed to open the safe is being investigated by the police.

为了保持句子结构平衡，有时须用it作形式主语，而将主语从句后置。

It is strange that she should reject the invitation.

It is quite clear that she doesn't yet know the facts.

B）       宾语从句 ( object clause)

He thinks, I’m afraid, (that) he is always in the right.

Everyone could see (that) the girl was not to blame.

She asked me whether there would be any meeting in the afternoon.

C）       补语（表语）从句 (complement / predicative clause)

That was how he solved the problem.

That’s why she is absent from school.

The problem is who can help him out of his difficulties.

l  补语从句与同位语从句（appositive clause）

---- The fact is that he is guilty of a serious blunder.

---- The fact that he is guilty of a serious blunder should not be ignored.

---- My idea is that effective measures must be taken to combat pollution.

---- I have long had an idea that effective measures must be taken to combat pollution.

2．    带状语分句的复杂句

状语分句可以表示时间、处所、方式、原因、目的、结果、条件、让步等意义。

A）    时间状语分句( adverbial clause of time)

能引导时间状语分句的连词有 when(ever), while, as, before, after, since, till / until, as soon as, as long as, no sooner…than, hardly / scarcely…when等

When / whenever / every time Susan goes to town, she will visit her grandparents.

The children kept cheering as long as the game continued. 

B）    地点状语分句( adverbial clause of place)

地点状语分句通常由where, wherever引导。

The hotel will be built where there used to be a church.

The boy is praised by people wherever he goes.

C）    方式状语分句( adverbial clause of manner)

方式状语分句通常由as, as if, as though引导

When in Rome , do as the Romans do.

He behaves as if / as though he were the duke himself.

D）    原因状语分句( adverbial clause of cause)

原因状语分句通常由because，as，since引导。其中because，as，since引导。其中because语势最强，since次之，as又次之。Because通常表示未知原因， 而since和as则表示已知原因。

Mary didn’t go shopping, because I advised her not to.

Since a quorum is not present, no votes may be taken.

As he was ill, our boss had cancelled the appointment.

E）    目的状语分句 (adverbial clause of purpose)

目的状语分句通常由so that和in order that 引导。

You ought to make a note of it so that you won’t forget.

They work hard in order that they might succeed.

F）     结果在状语分句 (adverbial clause of result)

结果状语分句通常由so that， with the result that引导。

He had overslept, so that he was late for work.

I was in the bath, with the result that I didn't hear the knock.

G）    条件状语分句 (adverbial clause of condition)

条件状语分句通常由if, unless, provided / providing(that), in case, so / as long as等引导

I will go providing it doesn’t rain.

As long as you ask him beforehand, he won’t object.

In case such a misfortune should befall us again, we must go to the court.

H）    让步状语分句 (adverbial clause of concession)

让步状语分句通常由though， although等引导。除 though，although外， 让步状语分句还可由if, even if, whatever, however, no matter what / how /when等引导。

Father is still teaching, though / although he is getting old.

Though everybody deserts you, I will not.

Even if it rains tomorrow, I will start off.

No matter when he arrives, we still wait fir him.