复合句分为并列复合句compound sentence（也称并列句）和主从或从属复合句complex sentence（也称复杂句），并列复合句compound sentence是有并列连词：and、or、but连接；从属复合句complex sentence由一个主句（Principal Clause）和一个或一个以上的从句(Subordinate Clause)构成。用疑问词作引导词，主句是全句的主体，通常可以独立存在；从句则是一个句子成分，不能独立存在。从句不能单独成句，但它也有主语部分和谓语部分，就像一个句子一样。所不同在于，从句须由一个关联词（conjunction）引导。 根据引导从句功能不同，大致可分为：主语从句、表语从句、宾语从句、定语从句、状语从句等。

从属复合句可分为：

(1).定语从句（The Attributive Clause）；

(2).状语从句（The Adverbial Clause）；

(3).名词性从句（The Noun Clause）；

定语从句的定义

定语从句在句中作定语，用来修饰一个名词、名词词组或者代词。

先行词和引导词

被修饰的名词、名词词组或代词叫做先行词；

在先行词和定语从句之间起连接作用的词叫做引导词。

引导词分为“关系代词”和“关系副词”。

关系代词和关系副词

关系代词有：who, whom, whose, that, which, as。

关系副词有：when, where, why。 注意：关系副词里面没有how。

如果要修饰方式，用that或in which引导，或者不用引导词。

I don’t like the way (不用引导词.that, in which) he eyed me.

我不喜欢他看我的那个样子。

关系代词

关系代词who在从句中主要作主语，在非正式语体里who还可以作从句中的宾语。

He is the man who wants to see you.

He is the man who I saw in the park yesterday.

关系代词

He is the man（whom）I saw in the park yesterday.

（whom在从句中作宾语）

关系代词

whose 用来指人或物，（只能用作定语, 若指物，它还可以同of which互换）。

They rushed over to help the man whose car had broken down.

Please pass me the book whose cover is green. （of which the cover/the cover of which）

关系代词

which指物，在从句中作主语或宾语，作宾语时在非正式语体中可以省略。

They needed a plant which didn't need as much water as rice.

The farm (which)we visited yesterday is located in the suburb of Beijing.

关系代词

当在which和that面前进行选择的情况下，一般情况下要选which：

1.在非限制性定语从句中通常用which作引导词，而不能用that做非限制性定语从句的引导词。

2. 修饰整个主句。

I never met Julia again after that, which was a pity.

3. 修饰谓语部分。

He can swim in the river, which I cannot.

4.介词+ which

They are all questions to which there are no answers.

关系代词

that多用来指物，有时也可以用来指人；在从句中作主语或宾语。指物的时候多用that，也可用which。

It’s a question that (which)needs careful consideration.

（指物，作主语。）

Who is the man that is reading a magazine under the tree?

（指人，作主语。）

The girl (that)we saw yesterday is Tom’s sister.

（指人，作宾语，可省略。）

关系代词

在以下的情况中，只能用that作引导词，而不能用which作引导词。

1.先行词为all , everything, anything, nothing, little等不定代词时。

All(that)she lacked was training.

2.先行词被形容词最高级修饰时

This is the best film that I have ever seen.

3.先行词被序数词和the last修饰时

4.先行词中既有人又有物时

They talked about the teachers and the schools that they had visited.

5.主句是含有who或which的特殊疑问句，为了避免重复时

地点状语从句通常由where, wherever 引导。

Where I live there are plenty of trees.

Wherever I am I will be thinking of you.

方式状语从句通常由as, (just) as…so…, as if, as though引导。

（1） as, (just) as…so…引导的方式状语从句通常位于主句后，但在(just) as…so…结构中位于句首，这时as从句

Always do to the others as you would be done by.

你希望人家怎样待你，你就要怎样待人。

As water is to fish, so is air to man.

我们离不开空气，犹如鱼儿离不开水。

Just as we sweep our rooms, so we should sweep backward ideas from our minds.

正如打扫房屋一样，我们也要扫除我们头脑中落后的东西。

（2） as if, as though

两者的意义和用法相同，引出的状语从句谓语多用虚拟语气

They completely ignore these facts as if (as though)they never existed.

他们完全忽略了这些事实，就仿佛它不存在似的。（与事实相反，谓语用虚拟语气。）

He looks as if (as though)he had been hit by lighting.

他那样子就像被雷击了似的。（与事实相反，谓语用虚拟语气。）

It looks as if the weather may pick up very soon.

看来天气很快就会好起来。（实现的可能性较大，谓语用陈述语气。）

说明：as if / as though也可以引导一个分词短语、不定式短语或无动词短语，例如：

He stared at me as if seeing me for first time.

他目不转睛地看着我，就像第一次看见我似的。

He cleared his throat as if to say something.

他清了清嗓子，像要说什么似的。

比较：because, since, as和for

（1） because语势最强，用来说明人所不知的原因，回答why提出的问题。当原因是显而易见的或已为人们所知，就用as或 since。

I didn't go, becauseI was afraid.

Since /As the weather is so bad, we have to delay our journey.

（2） 由because引导的从句如果放在句末，且前面有逗号，则可以用for来代替。但如果不是说明直接原因，而是多种情况加以推断，就只能用for。

He is absent today, because / for he is ill.

He must be ill, for he is absent today.

表示目的状语的从句可以由that, so that, in order that, in case等词引导，例如：

You must speak louder so that /in order that you can be heard by all.

Better take more clothes in case the weather is cold.

结果状语从句常由so… that 或 such…that引导，掌握这两个句型，首先要了解so 和 such与其后的词的搭配规律。

比较：so和 such

其规律由so与such的不同词性决定。such 是形容词，修饰名词或名词词组，so 是副词，只能修饰形容词或副词。 so 还可与表示数量的形容词many, few, much, little连用，形成固定搭配。

sofoolish, such a fool

sonice a flower, such a nice flower

somany / few flowers, such nice flowers

somuch / little money, such rapid progress

somany people, such a lot of people

（ so many 已成固定搭配，a lot of 虽相当于 many，但 a lot of 为名词性的，只能用such搭配。）

so…that与such…that之间的转换既为 so与such之间的转换。

The boy is so young that he can't go to school.

He is such a young boy that he can't go to school

连接词主要有 if, unless, as/so long as, on condition that 等。.

if 引导的条件句有真实条件句和非真实条件句两种。非真实条件句已在虚拟语气中阐述。

unless = if not.

Let's go out for a walk unless you are too tired.

If you are not too tired, let's go out for a walk.

连接时间状语从句的连接词有：when, before, after, while, as soon as, until, since...... 这里要注意一点的 是，如果主句是一般将来时，从句只能用一般现在时表示将来意义。

though, although

注意：当有though, although时，后面的从句不能有but，但是 though 和yet可连用

Although it's raining, they are still working in the field.

(3) even if, even though. 即使

We'll make a trip even though the weather is bad.

(4) whether…or- 不管……都

Whether you believe itornot, it is true.

No matter what happened, he would not mind.

Whatever happened, he would not mind.

替换：no matter what = whatever

no matter who = whoever

no matter when = whenever

no matter where = wherever

no matter which = whichever

no matter how = however

注意：no matter 不能引导主语从句和宾语从句。

（错）No matter what you say is of no use now.

（对）Whateveryou say is of no use now.（无论你说什么都是无用的）

你现在说什么也没用了。(Whatever you say是主语从句)

（错）Prisoners have to eat no matter what they're given,

（对）Prisoners have to eat whateverthey're given. 囚犯们只能给什么吃什么。

比较while, when, as

（1）as, when 引导短暂性动作的动词。

Just as / Just when / WhenI stopped my car, a man came up to me.

（2）当从句的动作发生于主句动作之前，只能用when 引导这个从句，不可用as 或 while。

Whenyou have finished your work, you may have a rest.

（3）从句

Asthe day went on, the weather got worse.

日子一天天过去，天气越变越坏。

比较until和till

判断句中的动词该用肯定式还是否定式。

肯定句：

I slept untilmidnight. 我一直睡到半夜时醒了。

Wait tillI call you. 等着我叫你。

（在肯定句中可用before代替 Let's get in the wheat beforethe sun sets.）

否定句：

She didn't arrive until6 o'clock.

Don't get off the bus untilit has stopped.

(1)Until可用于句首，而till通常不用于句首。

Untilyou told me, I had heard nothing of what happened.

直到你告诉我以前，出了什么事我一点也不知道。

(2)Until when疑问句中，until要放在句首。

---Until whenare you staying? 你待到什么时候？

---Untilnext Monday. 待到下周一。

注意：否定句可用另外两种句式表示。

(1)Not until …在句首，主句用倒装。

Not untilthe early years of the 19th century did manknow what heat is.

直到19 世纪初，人类才知道热能是什么。

Not untilI began to work did Irealize how much time I had wasted.

直到我开始工作，我才认识到了我已蹉跎了几多岁月。

(2) It is not until… that…

I had hardly / scarcelygot home whenit began to rain.

I had no soonergot home thanit began to rain.

As soon asI got home, it began to rain.

注意：如果hardly, scarcely 或no sooner置于句首，句子必须用倒装结构：

Hardly / Scarcely had Igot home when it began to rain.

No sooner had Igot home than it began to rain.

在复合句中充当主语成分的句子叫做主语从句。常规主语从句，即句子在复合句中充当一个主语。主语从句的时态：不受主句的时态影响和限制。（1）That he finished writing the composition in such a short time surprised us all.（2）Whether we will go for an outing tomorrow remains unknown.（3）Who will be our monitor hasn't been decided yet.（4）Whom we must study for is a question of great importance.（5）What caused the accident remains unknown.（6）Whatever you did is right.（7）Who the watch belongs to is unknown.（8）What we need is time.（9）What we need are good doctors.小结:（1）引导主语从句连词有that,whether,who,what,whatever等（2）连词位于句首不能省略（3）主语从句大多数情况下视为第三人称单数，但也有例外，如例（9）

注意：当what引导的名词性分句作主语时，主谓一致问题极为复杂。著名学者周海中教授在论文《关于what-分句作主语的主谓一致问题》中就这一问题做了深入研究，并给出了10种的主谓一致关系。这些一致关系值得英语学习者和使用者特别注意。

在句子中起宾语作用的从句叫做宾语从句。宾语从句的引导词和主语从句的引导词相同。宾语从句可以作及物动词的宾语，作短语动词的宾语，介词的宾语。

宾语从句的引导词有三种情况:

（1）引导陈述意义的 句子用that，无实际意义，口语中可以省略。

（2）表示“是否”的 意义时用whether或if （当句中有or是只能用whether而不用if）

（3）引导特殊疑问句意义的句子时用特殊疑问词who, whose, whom, which, what, when, where, 或how.

宾语从句的语序:无论什么引导词，表达陈述还是疑问，宾语从句都必须用陈述语序。

宾语从句的时态:

主句是一般现在时，从句根据需要选用相应的时态，主句的谓语是一般过去时，从句的谓语动词在时态上要用相应的过去时态，（若从句表示的 是客观真理或自然现象，不论主句时态，从句都用一般现在时态）。

·宾语从句：及物动词的宾语

Everybody knows that money doesn't grow on trees.

·宾语从句：短语动词的宾语

Please go and find out when the train will arrive.

·宾语从句：介词的宾语

I am interested in what she is doing.

·宾语从句：否定的转移

I don't suppose you're used to this diet.

我想你不习惯这种饮食。

·表语从句

在句子中起表语作用的从句叫做表语从句。表语从句的引导词和主语从句的引导词相同。

What the police want to know is when you entered the room.

This is what we should do.

That's why I want you to work there.

as if, as though, because也可用来引导表语从句。

She seems as if she had done a great thing.

It is because you eat too much.

·虚拟语气：表语从句

主语是idea, notion, proposal, suggestion, request等名词时,作表语从句的动词为原形动词或should+原形动词。

My suggestion is that we (should)go and help him.

Our only request is that this shouldbe settled as soon as possible.

·同位语从句一般跟在某些名词如answer(答案)，hope(希望)，fact(事实)，belief (信仰)，news(消息)，idea(主意；观念)，promise(承诺)，information(信息)，conclusion(结论)，order(命令)， suggestion(建议)，problem(问题)，thought (想法)等后面。例如：

I had no idea thatyou were here.

She told us her hope thatshe would become a pianist.

He made a promise thathe would never come late.

·同位语从句：whether

whether可以引导同位语从句，而定语从句不能用whether作为引导词。

He hasn’t made the decision whetherhe will go there.

I have small doubt whetherhe is suitable for the job.

·同位语从句：what

what可以引导同位语从句，而定语从句不能用what作为引导词

I have no idea whathe is doing now.

·同位语从句：how

how可以引导同位语从句，而定语从句不能用how作为引导词

It’s a question howhe did it