状语从句在复合句中，用作状语的从句叫状语从句。

状语从句根据它表达的意义可以分为：时间状语从句、地点状语从句、原因状语从句、结果状语从句、让步状语从句、条件状语从句、目的状语从句、比较状语从句、方式状语从句。

（1）时间状语从句引导时间状语从句的连词或短语有：when, while, as, before, after, since, until, as soon as, once, each time, next time等。

1.When引导的时间状语从句When引导时间状语从句时，意为“当....时”，表示主句的动作与从句的动作同时或先后发生。

例：When you are doing your homework, you must be careful.Someone knocked（敲）at the door when I was sleeping.When she first saw the robot, she felt astonished（惊讶）.When Tom got home, he wept with anger.注意：when引导的时间状语从句中的动词可以是延续性的，也可以是非延续性的。

2.while引导的时间状语从句while引导的时间状语从句，意为“与...同时；在...期间”例：They entered the room while we were discussing problems.Father was cleaning the car while I was playing computer games.When she was in college, she felt in love with Mike.注意：while引导的时间状语从句中的动词必须为延续性或者表示状态的动词。

3.as引导的时间状语从句as引导的时间状语从句，表达“正当...，一边...一边...”强调主从句动作同时发生。

例：I heard their voice as I cross the hall（走廊，过道）.As she sang, the tears ran down her cheek（脸颊）.As I waited at the stop, I heard a big noise.4.before引导的时间状语从句before意为“在...之前”,引导时间状语从句，表示主语的动作在从句前发生。

例：We cleaned the classroom before we left school yesterday.It’ll not be long before you regret（后悔）what you’ve done.5.after引导的时间状语从句after意为“在...之后”,引导时间状语从句，表示主语的动作在从句后发生。

例：He called me after he had finished his homework.She usually takes a walk after she has dinner.6.since引导的时间状语从句Since常意为“自从......”主句常用现在完成时，从句用一般过去时。

例：Everything has changed since I was here.I haven’t heard from him since he moved away.常用句型：It is/has been+时间段+since从句，意为“自从....已经多少时间”例：It has been three years since I moved to Beijing.自从我搬到北京已经有两年的时间了。

7.till和until导的时间状语从句Till和until用于肯定句时，主句动词为延续性动词，意为“直达...才”表示“某动作或状态一直持续到某时间点才停止”；用于否定句时，主句动词是非延续性动词。

注意：无论用于肯定或否定，从句都为肯定句。

例：I will stay here until you come back.He won’t go to bed until she returns.8.as soon as引导的时间状语从句as soon as 意为“一...就...”表示从句的动作一发生，主句的动作马上发生。

例：As soon as he heard the news（消息，新闻）, he jumped with joy.他一听说那个消息，就开心地跳了起来。

I’ll write to you as soon as I get there. 我一到那儿就给你写信。

He contacted（联系）us as soon as he arrived in Shanghai. 他一到上海就和我们取得联系。

9.by the time引导的时间状语从句by the time意为“到...时候”，由by the time引导的时间状语从句要注意时态的变化：一般情况下，如果从句的谓语用一般过去时（did），那么主句的谓语用过去完成时（had done）。

例：By the time you came back, I had finished this program.By the time I arrived at the bus station, the bus had already left.（2）原因状语从句引导原因状语从句的连词主要有：because, as, since, for, now that等。

1.because引导的原因状语从句because引导原因状语从句意为“因为”，表因果关系的语气最强，用来回答why的问句，because引导的原因状语从句往往比主句显得更重要。

例：I stayed at home, because it rained.Tom didn’t come to school, because he is ill.We won the game, because we have strong players.2.since引导原因状语从句Since引导原因状语从句表示人们已知的事实，不需强调原因，常译为“既然”。

Since引导的从句是次要的，主要强调主句的内容。

例：Since he was busy, he didn’t come.Since you are free today, why not play chess with me.3.as引导的原因状语从句as和since的用法差不多，所引出的原因对于说话者看来已经很显然，或已成为听话人所熟悉的，不需要用because加以强调。

例：As Monday is the National Holiday（国庆节）, all government offices will be closed.I have to speak English with them as they don’t know any Chinese.4.for引导的原因状语从句for引导的原因状语从句只能跟在主句的后面，相当于汉语的“其理由是”。

例：I stopped to rest, for I was very tired.The days are short, for it is December now.（3）条件状语从句条件状语从句的连词或短语有：if, unless, so/as long as等。

1.if引导的条件状语从句if是引导条件状语从句最常用的连词，意为“如果”。

例：If you travel in India（印度）, you can use English everywhere.I’ll tell you about it, it you come.My parents will take me to the park if they are free.2.unless引导的条件状语从句Unless意为“除非...要不然”。

意思相当于“if not”例：You’ll fail in the exam unless you study hard.You’ll miss（错过）the train unless you get up early.3. as/so long as引导的条件状语从句as/so long as引导条件状语从句，意为“只要”例：You can keep the book as long as you like.You can use my room as long as you keep it clean.I am happy as long as you are happy.（4）结果状语从句引导结果状语从句的连词有：so that, so...that..., such...that...等。

1.so that引导的结果状语从句so that引导结果状语从句，意为“因此，所以”例：She was ill so that she cant get out of bed. 他病了，下不了床了2.so...that.../such...that引导的结果状语从句so...that...和such...that引导结果状语从句，都意为“如此...，以至于...”注意：这两个短语虽意思相同，但使用方法不同，so为副词，其后可跟形容词或副词，而such为形容词，其后只可跟名词。

①so...that..常见结构如下：so+形容词/副词+that例：Mary is so lovely that we all like to play with her.so+形容词+a(an)+单数名词+that例：It is so hot a day that nobody wants to do anything.so+many/few+复数名词+that例：There are so many people that we are hard to move.so+much/little+不可数名词+that例：There is so little time that we have to speed up（加速）.②such...that...常见结构如下：such+a(an)+形容词+可数名词单数+that例：Mary is such a lovely girl that we all like to play with her.such+形容词+可数名词复数+that例：These are such difficult questions that none of us could answer them.such+形容词+不可数名词例：We had such terrible weather that we couldn’t finish the work on time.（5）目的状语从句引导目的状语从句的连词有：so that, in order that等。