在复合句中作状语的从句叫做状语从句。状语从句主要用来修饰主句谓语（或其它动词）、形容词、副词或是整个主句。一般可分为九大类，分别表示时间、地点、原因、目的、结果、条件、让步、比较和方式。尽管种类较多，但由于状语从句与汉语结构和用法相似，所以理解和掌握它并不难。状语从句的关键是要掌握引导不同状语从句的常用连接词和特殊的连接词。
一、时间状语从句
常用引导词：when, as, while, as soon as, while, before, after, since , till, until
特殊引导词：the minute, the moment, the second, every time, the day，the instant, immediately , directly, no sooner … than, hardly …when, scarcely … when
I didn’t realize how special my mother was until I became an adult.
While John was watching TV, his wife was cooking.
The children ran away from the orchard the moment they saw the guard.
Every time I listen to your advice, I get into trouble.
二、地点状语从句
常用引导词：where
特殊引导词：wherever, anywhere, everywhere
Generally, air will be heavily polluted where there are factories.
Wherever you go, you should work hard.
三、原因状语从句
常用引导词：because, since, as, since
特殊引导词：seeing that, now that, in that, considering that, given that, considering that,
My friends dislike me because I’m handsome and successful.
Now that everybody has come, let’s begin our conference.
The higher income tax is harmful in that it may discourage people from trying to earn more.
Considering that he is no more than 12 years old, his height of 1.80 m is quite remarkable.
四、目的状语从句
常用引导词：so that, in order that
特殊引导词：lest, in case, for fear that，in the hope that, for the purpose that, to the end that
The boss asked the secretary to hurry up with the letters so that he could sign them.
The teacher raised his voice on purpose that the students in the back could hear more clearly.
五、结果状语从句
常用引导词：so … that, so… that, such … that,
特殊引导词：such that, to the degree that, to the extent that, to such a degree that,
He got up so early that he caught the first bus.
It’s such a good chance that we must not miss it.
To such an degree was he excited that he couldn’t sleep last night.
六、条件状语从句
常用引导词：if, unless,
特殊引导词：as/so long as, only if, providing/provided that, suppose that, in case that, on condition that
We’ll start our project if the president agrees.
You will certainly succeed so long as you keep on trying.
Provided that there is no opposition, we shall hold the meeting here.
七、让步状语从句
常用引导词：though, although, even if, even though
特殊引导词：as(用在让步状语从句中必须要倒装)，while ( 一般用在句首 )，no matter …， in spite of the fact that, while, whatever, whoever, wherever, whenever, however, whichever
Much as I respect him, I can’t agree to his proposal.
尽管我很尊敬他，我却不同意他的建议。
The old man always enjoys swimming even though the weather is rough.
No matter how hard he tried, she could not change her mind.
He won’t listen whatever you may say.
八、比较状语从句
常用引导词：as(同级比较), than(不同程度的比较)
特殊引导词：the more … the more … ; just as …， so…; A is to B what /as X is to Y; no … more than; not A so much as B
She is as bad-tempered as her mother.
The house is three times as big as ours.
The more you exercise, the healthier you will be.
Food is to men what oil is to machine. 食物之于人，犹如油之于机器。
九、方式状语从句
常用引导词：as, as if, how
特殊引导词：the way
When in Rome, do as the Roman do.
She behaved as if she were the boss.
Sometimes we teach our children the way our parents have taught us.
十、状语从句的简化
状语从句的省略
状语从句同时具备下列两个条件:①主句和从句的主语一致，或从句主语为it；②从句主要动词是be的某种形式。从句中的主语和be动词常可省略。例如：
When ( the museum is ) completed , the museum will be open to the public next year .
He’ll go to the seaside for his holiday if (it is ) possible.
另外，比较状语从句经常省略。例如：
I’m taller than he (is tall ).
The higher the temperature (is), the greater the pressure (is ).
就状语从句而言,有时为了使语言言简意赅,常常将状语从句进行"简化"。状语从句的"简化"现象在口语中较为普遍,而且在高考中的复现率也较高。因此,有必要对其进行全面、透彻的了解。
状语从句的"简化"现象常存在于以下五种状语从句中:①由if, unless等引导的条件状语从句;②由although, though, even if / though等引导的让步状语从句;③由when, while, as, before, after, until / till等引导的时间状语从句;④由as, as if等引导的方式状语从句;⑤由as, than等引导的比较状语从句。下面针对这五种情形作一归纳。
1. 当状语从句的主语是it,且谓语动词是be时,it和be要完全简化掉。例如:
If (it is) possible, he will help you out of the difficulty. 如果可能的话,他会帮你摆脱困境。
You must attend the meeting unless (it is) inconvenient to you. 除非情况对你来说不方便,否则你必须出席这次会议。
2. 当状语从句的主语和主句的主语一致时,从句可以将主语和be动词简化掉。常用于以下几种情形:
1）连词+形容词
As (he was) young, he learned how to ride a bike. 他小时候就学会了骑自行车。
Whenever (she is) free, she often goes shopping. 她有空就去逛商店。
Work hard when (you are) young, or you'll regret. 少壮不努力,老大徒伤悲。
2）连词+名词
While (he was) a young boy, he was always ready to help others. 他在孩提时代就乐于助人。
Although (he was) a farmer, now he is a famous director. 尽管他曾是个农民,而现在是位著名的导演了。
3）连词+现在分词
As (she was) walking along the river bank, she was singing a pop song. 她沿着河堤边走边唱着流行歌曲。
Although (he is) doing his best in maths these days, he has still got no good marks. 尽管近来他一直在学数学,但他仍然没有取得好成绩。
4）连词+过去分词
He won't go there with us unless (he is) invited. 除非受到邀请,否则他不会和我们一道去那里。
The concert was a great success than (it was) expected. 这场音乐会出乎意料地取得了巨大成功。
e. 连词+不定式
He stood up as if (he were) to say something. 当时他站起来好像要说什么。
He wouldn't solve the problem even if (he were) to take charge. 即使他来负责,他也解决不了这个问题。
5）连词+介词短语
She looked anxious as though (she was) in trouble. 她看上去很焦急,好像遇到了麻烦。
He had mastered the English language before (he was) in the USA. 他到美国之前就懂英语了。
注意:当从句主语和主句主语不一致时,从句部分要么用完全形式,要么用独立主格结构来表达。例如:
When the meeting was over, all the people went out of the meeting-room. 当会议结束时,人们都走出了会议室。（= The meeting over, all the people went out of the meeting-room.）