状语从句在句中作状语，修饰主句中的动词、形容词或副词等。状语从句放在主句之前时，常用逗号分开；放在主句之后，一般不用逗号。状语从句按其意义和作用可分为时间、原因、条件、、让步、地点、目的、结果、方式、比较等九种。
1．时间状语从句
时间状语从句通常由when, while, as, before, after, (ever) since, till, until, as soon as等从属连词引导。
When he was skating round the lake, he suddenly fell.
I haven’t heard from him since he left school.
As soon as he appeared on the stage, the audience began to cheer.
注意：时间状语从句中用一般现在时表示将来意义。例如：
I will go on with the work when I come back tomorrow.
I will send you email as soon as I reach New York.
1）when, while, as引导时间状语从句时的异同
when引导的时间状语从句中的谓语动词既可以是延续性动词，也可以是短暂性动词；从句的动作可以和主句的动作同时发生，也可以先于主句的动作发生，此时相当于after。当when从句谓语动词是延续性动词时，可与while互换。
I often missed my home a lot when I was abroad.. ( =while )
When they came home, I was cooking dinner. (不能用while)
When the film ended, people rushed out of the hall. ( =after )
when从句置于主句后面，同时从句中谓语动词又是短暂性动词时，常表示“此时突然……”。
I was walking along the street when I caught sight of a tailor’s shop.
He was enjoying his dinner when a loud noise came on the door.
while引导的动作必须是持续性的，强调主句和从句动作的同时发生，有时侧重主句和从句动作的对比。
He took a bath while I was preparing dinner.
as常可与when, while通用，但它较强调主句和从句动作的同时发生，常译作“边……边”也可用来说明两种正在发展和变化的情况，此时常译作“随着”。
He sang happily as he walked along the path.
The day gets longer and longer as summer comes.
2）until, till引导的时间状语从句
主句谓语动词为延续性动词时，主句和从句都用肯定句式，意为“一直到”，表示主句动作一直延续到until/till从句表示的时间才终止；主句谓语动词为短暂性动词时，主句用否定式，从句用肯定式，意思是“一直到才”，表示主句动作到until/till从句表示的时间才开始。
He worked until/till it was dark.
He didn’t work until/till it was dark.
until和till意义相同，通常可换用，但在强调结构、倒装句或句首，一般用until。例如：
I didn’t know about it until/till he told me.
It was not until he told me that I knew about it.
Not until he told me did I know about it.
3）since引导的时间状语从句和before引导的时间状语从句
since从句中的动词不同，其起算时间也不同。since + 瞬间动词过去时，从该动作发生时起算；since + 延续性动词过去时，从该动作结束时起算。试比较：
He has worked very hard since he entered the factory.
(enter为瞬间性动词，该句意为“从他入厂以来，他工作一直非常努力。”)
We haven’t seen each other since I worked in the factory.
(work为延续性动词，该句意为“从我不在工厂以来，我们没见过面。”可说成
We haven’t seen each other since I stopped working in the factory.）
since常用于It’s + some time + since sb. did sth.结构。试比较：
It’s two years since he joined the army. （他参军有两年了。）
It’s two years since he was a soldier. （他退役有两年了）
before有时可译为“还没……就”。如：
He had measured me before I could say a word. （我还没来得及说话他就给我量好了尺寸。）
I hadn’t waited long before he came. （我还没等多久他就来了。）
I slipped out before the lecture started. （还没等讲座开始我就溜了出去。）
before也可用于it结构，与since结构比较相似，注意它们所用时态的区别，其结构通常是
It will be + some time + before sb. does sth. 或It was + some time + before sb. did sth.. 可表示将来或过去两个概念。常译作“……才……”。例如：
He is leaving for Australia and it will be three years before he comes back.
(他要去澳大利亚了,三年后才会回来。)
(Duing the war he joined the army and it was three years before he came back.
（战争期间他参了军，三年后才回来了。）
4）as soon as等意为“一……就”的时间状语从句的几种不同表达
as soon as表示“一……就”，在表述已发生的动作时，hardly…when, no sooner…than也可表示同样的意思，但主句谓语动词要用过去完成时，从句用过去时，还可转换成倒装结构。
As soon as he saw the policeman, he ran away.
= He had hardly seen the policeman when he ran away.
= Hardly had he seen the policeman when he ran away.
= He had no sooner seen the policeman than he ran away.
= No sooner had he seen the policeman than he ran away.
immediately, directly, instantly, the moment, the minute, the instant,也可引导时间状语从句，相当于as soon as的意思，用法也与as soon as基本相同。上述句子可转换成：
He ran away immediately/directly/instantly he saw the policeman.
He ran away the moment/the minute/the instant he saw the policeman.
5）the moment, the minute, the instant, the day, the year, the first time, last time, each/every time, next time, by the time等少数表示时间概念的短语也可引导时间状语从句。例如：
I recognized her the minute I saw her.
Her son was born the day Hongkong returned to its motherland.
He left Europe the year World War Ⅱ broke out.
He was attracted by the beauty of the city the first time he went there.
Last time I saw her, she was writing a book.
Don’t refer to the dictionary each/every time you come upon a new word.
I will go to the seaside next time I go to Dalian.
He had finished learning advanced mathematics by the time he was 14.
2．原因状语从句
1）原因状语从句通常由because, since, as引导。because引导的从句可以放在主句前，也可放在主句后面，表示直接的原因或理由，着重点在从句。回答why问句、用于强调结构都用because。如：
He had to do a part-time job after work because he needed money for his marriage.
---Why didn’t he come yesterday?
---Because he had something important to do.
It was because he lost it that he found it more valuable than ever.
since和as引导的原因从句更多见于句首，表示明显的、已知的事实，语气比because弱，分别可译作“既然”、“由于”，着重点在主句。
Since you have to stay at home, why don’t you do some shopping on computer?.
As the weather is fine, let’s go fishing.
for也可引导表示原因的句子，但它是个并列连词，通常表示一种推测的原因或附加的说明，语气最弱，一般不放在句首，前面常有逗号分隔。
It must have rained last night, for the ground is wet.
2）now that, seeing that, considering that等也可以引导表示原因的从句, 语气相当于since，常译作“既然”，口语中that可省去。例如：
Now (that) my watch has been sold, what’s the use of the watch chain?
Seeing (that) you’re already at the door, I suppose I must invite you inside.
3．条件状语从句
条件句可分为真实条件句和非真实条件句，非真实条件句在虚拟语气中有详细表述，这里只讨论真实条件句。引导条件句常用的有if, unless, as(so) long as, in case等，when, once, suppose (that) 或supposing (that)，on condition that 也可引导表示条件的从句。条件状语从句和时间状语从句一样，表示将来要用一般现在时。例如：
The bell is rung if there is a fire.
We won’t let you in unless you show your pass.
You may use my bike as/so long as you return it before Friday.
In case anything important happens, please call me up.
Turn off the switch when anything goes wrong.
Once you taste the noodles, you’ll never forget their delicious flavour.
Suppose/Supposing (that) you fail again this time, what will you do?
He agreed to lend him the money on condition that he paid back three times more money in three months’ time.
4．让步状语从句
1）通常由though, although, even/though引导，主句中不能用but，但可用yet。如：
He didn’t light the fire though/although it was cold.
Although/though he is quite old, (yet) he still tries to learn more.
I’ll try to finish the work myself even if/though it takes me days.
3） whatever, whoever, whichever, whenever, wherever, however 引导状语从句时，分别相当于no matter what/who/which/when/where/how引导的从句，意为“无论……”。例如：
Whatever/No matter what he said, no one believed him.
Whoever/No matter who breaks the law, he will be punished.
Whichever/No matter which job you take, you should try to do well in it.
Whenever/No matter when I need his help, he comes immediately.
Wherever/No matter where you go, never forget your motherland.
However/No matter how busy he was, he would watch TV sports news every night.
注意whatever, whoever, whichever又可引导名词性从句，注意区别。可参阅本章第一节。
3）as引导让步状语从句要倒装，其结构通常是“noun/adj/adv + as + 主语+谓语(+其它成分)，主句”，可转换成though/although从句。
Child as he is, he knows a lot. （注意：名词前不用冠词）
=Although/Though he is a child, he knows a lot.
Difficult as the task was, they managed to finish it in time.
=Although/Though the task was difficult, they managed to finish it in time.
Much as I like it, I will not buy it.
=Although/Though I like it much, I will not buy it.
偶尔也可见用动词提前的让步状语从句。例如：
Try as he may, he can hardly do better than she.
=Although/Though he may try, he can hardly do better than she.
4）whether…or也可引导让步状语从句，相当于“no matter whether…or”。
Whether you come in winter or in summer, you will find it a nice place.
=No matter whether you come in winter or in summer, you will find it a nice place.
5．地点状语从句
1）地点状语从句常由where和wherever引导，通常可置于主句之前或之后。。
I found the books where I left them.
Make a mark where you have any questions.
We should go where(ver) we are most needed.
Where there is a will, there is a way.
Where there is water, there is life.
2）where引导的状语从句和where引导的定语从句常可转换，判断它属于哪类从句的关键是看where前面有没有被修饰的、表示地点的先行词。试比较：
Stand where you are! （状语从句）
Stand at the place where you are! （定语从句）
Bamboo grows best where it’s wet and rainy. （状语从句）
Bamboo grows best in places where it’s wet and rainy. （定语从句）
6．目的状语从句
1）目的状语从句通常由 (so) that, in order that引导,在口语或非正式文体中，有时也会用that或so引导。in order that 引导的目的从句可以放在主句后面，也可放在主句前面，而so that引导的从句通常放在主句后面。目的状语从句中的谓语常含有may(might), can(could), should, will等情态动词。例如：
He always takes a seat in the first row so that/in order that he can hear better.
（也可说成He always takes a seat in the first row so/that he can hear better.但用的较少。）
=In order that he can hear better, he always taked a seat in the first row.
The actress wore ordinary clothes in order that/so that she might not be recognized easily.
=In order that she might not be recognized easily, the actress wore ordinary clothes.
2）in case, for fear that, lest 等也可以引导目的状语从句，表示 “以防…、以免…” 。如：
He left early in case he should miss the train.
Take your raincoat in case it rains/should rain.
Mother hid the sweets and chocolates lest/for fear that her son should see them.
7．结果状语从句
1）结果状语从句常由so that, so… that, such… that等引导，放在主句之后，so…that与such…that句型在一定条件下可转换。例如：
The lift was out of order, so that we had to walk to the 18th floor.
He was so angry that he left the room without saying a word.
He made such an excellent speech that everyone admired him.
=He made so excellent a speech that everyone admired him.
在口语中也可用that引导结果从句。例如：
What have I said that he should be so angry with me?
2）so that引导结果状语从句和目的状语从句的辨别
so that从句之前有逗号的常为结果状语从句，因表示某一行为带来的结果，从句中的时态常为过去式；so that从句中有may(might), can(could), should, will等情态动词的通常是目的状语从句。例如：
I wrote as clearly as possible so that I might get high marks. （目的）
I wrote as clearly as possible, so that I got high marks. （结果）
He went to the lecture early so that he could get a good seat. （目的）
He went to the lecture early, so that he got a good seat. （结果）
8．方式状语从句
1）方式状语从句常由 (just) as, as if/though引导，表示动作的方式。
Do exactly as the doctor says.
He walked slowly as if/though he had hurt his leg.
注：在非正式文体中有时会用like代替as引导方式从句。
2）as if/though 引导的状语从句，若描述非事实情况，常用虚拟语气，若描述的是实际情况，用陈述语气。例如：
She treats the orphan as if/though he were her own child.
（他是孤儿，当然就不是她的亲生孩子，故用虚拟语气。）
It looks as if/though it’s going to rain.
（本句用的是陈述语气，说明天真象是要下雨了。）
3）the way 也可用来引导方式状语从句。例如：
Mary smiled the way (in which/that) her mother did at her age.
（马丽跟她母亲在她那个年纪时笑起来一个样。）
9．比较状语从句
1）比较状语从句常由as … as, not so (as) … as, than引导。比较从句部分常为省略句。例如：
His brother is as handsome as he (is)/him. （非正式英语中可用宾格him）
He swims faster than any other student in his class (does).
2）通常把the more…the more…结构也归为比较从句，意为“越……越”。如：
The harder you work, the greater progress you’ll make.
The less she worred, the better she worked.
典型例题分析
1．If we work with a strong will, we can overcome any difficulty, ____ great it is. (’95)
A what B how C however D whatever
解析：本题考查-ever类词引导让步状语从句的用法。根据句意“无论困难有多大”，排除答案A/B，whatever=no matter what，后面跟名词或直接跟从句，however=no matter how，后跟形容词或副词，再接主语和谓语，故答案为C。
2．Mother was worried because Alice was ill, especially ____ Father was away in France. (’94)
A as B that Cduring D if
解析：根据前半句“妈妈因为Alice病了很着急”，后面有表示递进意义的词especially，顺着句意推测，应该是“尤其是因为父亲远在法国”，表示原因，故答案为A。注意during是介词，不能引导从句。
3．Why do you want a new job ____ you’ve got such a good one already? (’98)
A that B where C which D when
解析：本题考查when引导原因状语从句的特殊用法。本句意为“既然你已经有了一个好工作，为什么还要找份新工作呢？”A/B/C都没有表示原因的意思，不符合句意，故答案为D。
4．---What was the party like?
---Wonderful! It’s years ____ I enjoyed myself so much. (’93)
A after B before C when D since
解析：本题考查学生对”“It’s some time since sb. did sth.”结构的掌握，因一A/C般不用于此类句型，因此干扰最强的是before，而before常用句型为“It will be some time before sb. does sth.”，根据句子的意思及句中所用的时态，D为最佳选择。
5．We won’t give up ____ we should fail ten times. (’93)
A even if B since C whether D until
解析：解本题的关键是弄清空格前后两部分的关系，最佳的连接关系应该是“即使失败十次，我们也不放弃。” 符合句意的只有答案A。
6．John shut everybody out of the kitchen ____he could prepare his grand surprise for the party.
A which B when C so that D as if (2002)
解析：分析句子意思，发现“John把每个人都关在厨房外”的目的就是为了“能够准备他那别出心裁的晚会”，从句中的could是目的状语从句的标志，因此答案为能够引导目的状语从句的so that ( C )。
7．After the war, a new school building was put up ____ there had once been a theatre. (’97)
A that B where C which D when
解析：分析题干和选项，不难发现句子要表达的意思，“战后，在过去的剧院旧址上，新建了一所学校。”从空格到句末应该是一个表示地点的状语从句，故答案为B。
8．It is generally considered unwise to give a child ____ he or she wants. (97’)
A however B whatever C whichever D whenever
解析：本题句中从空格处到句末为一宾语从句，作give的直接宾语，因此排除答案A和D，而whichever引导名词性从句时， 所指代的名词应是已知范围内的人或物，通常在上文已经提到过或者在whichever后有该名词或of结构。Whatever在引导名词性从句时意为“anything that”，用于不定范围的情况，本句意为“一般认为孩子要什么就给什么是不明智的”，不确指什么东西，因此答案为B。
摘自《新编名师导学》
苏州市苏苑中学 许凤编写