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状语从句(adverbial clause)在句中作状语，可修饰主句中的动词、形容词和副词等。状语从句由从属连词引导。状语从句可放在句首或句末。放在句首时，从句后面常用逗号；放在句末时，从句
前面往往不用逗号。状语从句根据它们的含义分为时间、地点、原因、目的、结果、方式、让步、条件、比较等九种。
一、时间状语从句
1、while, when, whenever和as的用法比较
（1）while
常表示一段较长的时间或一个过程，强调主句的动词和从句的动词所表示的动作或状态是同时发生的。它不能表示一时性或短暂的动作。
Don't talk so loudwhile( as) others are working.别人工作时，请勿大声说话。
（2）when
引导的时间状语从句，可指时间的一点，也可以指一段时间，从句的谓语动词可用终止性动词，也可用持续性动词。when引导的从句表示的具体的时间，从句的动作和主句的动作可以同时，也可以先于主句的动作。Whenever指任何一个不具体的时间。
It was raining when we arrived. 我们到达时，天正下着雨。（动作同时，指时间点）
When you read the poem a second time, the meaning will become clearer to you.当你再读一遍这首诗，你就更清晰它的含意。（动作有先后，指时间点，不能用while）
Come whenever you like. 你爱什么时候来就什么时候来。
（3）as
用as时主句和从句的动作往往同时发生，具有延伸意义，一般同延续性动词连用，有时可译作“一边…一边…”。
As time went on, his theory proved to be correct.随着时间的推移，他的理论被证明是正确的。
As（when）he finished the speech,the audience burst into applause.他讲话结束的时候，听众掌声雷动。（指一点时间不能用while）
2、名词词组引导时间状语从句
有时名词every time(每次)，the next time(下一次)，the next day(第二天)，the moment(一……就……)， the instant, the second, the year等，也可起从属连词的作用，引导时间状语从句。
Every time you get back at night, you drop your shoes on the floor.你每一次晚上回来，都把鞋子丢在地板上。
3、副词作连词用引导时间状语从句
有些副词如instantly, immediately，instantly，directly, presently等也可起从属连词的作用，引导时间状语从句，表示"一……就……"的意思。
I recognized herinstantlyI saw her.我一看见她就把她认出来了。
4、since和before的用法比较
两者均可用于"It+ be...+since/before-从句"的句型。区别在于since表示“自从……以来”，所在主、从句的谓语动词的时态关系是:It is/has been sometime since sb. did sth.。而before的含义是 “(过了多久)才……”，主、从句的时态关系是:It was/had been some time before sb. did sth.。表过去和将来时，两者相应的句型分别是:It was some time since sb. had done sth.和It will be some time before sb. does sth.
It is 30 years since he joined the revolution. 他参加革命己三十年了。
It was three days before he came back. 他三天后才回来。
It was not long before he came back. 不久他就会来了。
二、地点状语从句
地点状语从句一般由where(在……地方; 那里)，wherever(无论哪里)和everywhere(在……每一个地方)引导。
After the war, a new school building was put up where there had once been a theatre. 战后，一所新学校在以前的剧院处建成。
You should make it a rule to leave things where you can find them again. 你应当养成惯例，将东西放在你能找到的地方。
She found her calculator where she lost it. 他在她丢的地方找到了计算器。
Everywhere they went, the distinguished guests were warmly welcomed.贵宾每到一处都受到了热烈的欢迎。
注意：where除了表示地点外，还可以表示条件、对比和让步。
Where there is a will, there is a way.有志者事竟成。（条件）
We want to stay at home, where children would rather spend the holiday in the country.我们想留在家里，而孩子们却愿到乡间度假。（对比）
Wherever I went, the dog followed me. 无论我走到哪里，这只狗总跟着我。（让步）
三、原因状语从句
原因状语从句一般由because(因为)，since(既然)，as(由于)，now that(既然，因为)等连词引导
1、because, since, as, for和now that引导原因状语从句
（1）because
表示直接的原因或理由，表示原因的语气最强，常表示必然的因果关系。回答以why引起的特殊疑问句，只能用because。
Jane wore a raincoat because it was raining.因为天下雨，所以詹穿着雨衣。
（2）since
表示对方已经知晓、无须加以说明的原因或事实，语气比because稍弱。
I'll do it for you since you are busy.既然你忙，我来替你做吧。
Since you insist, I'll go.既然你坚持，那我就去。
（3）as
表示的往往是十分明显的原因，听者或读者已经知道或能看得出来，语气较弱，只附带说明，比较口语化。
We had better hurry as it's getting dark.因为天快要黑了，我们最好快点。
As you object, I'll change the plan.由于你反对，我将改变计划。
（4）for
for是并列连词，它引导的分句不表示直接的原因，而是用来附带解释或说明前面一句的情况。for引导的分句常位于第一分句之后，它们之间用逗号隔开。
It must have rained last night, for the ground is wet this morning.昨晚准是下雨了，今天早上地面还是湿的。
The day breaks, for the birds are singing.小鸟在歌唱，一定是天亮了。
（5）now that
意为"既然"，与since同义，但更突出事实本身。
Now that everyone is here,let's begin our meeting.既然大家都来了，我们就开始开会吧。
Now that I am well again, I can go on with my work.我既然恢复了健康，那就可以继续工作了。
2、seeing that, considering that和in that引导原因状语从句
这几个连词同since, as 近义，都有“鉴于某个事实，原因”是之意。
Considering that he's only been learning English a year, he speaks it very well.鉴于他只学了一年， 他英语讲得就是很好。
Seeing that he was ill, they sent for the doctor.鉴于他病情严重，他们派人请医生。
In that she is ill, she feels unable to do it.因为病了，她觉得不能做那件事。
3、not that…but that…引导原因状语从句
这是一种加强语气的表示原因的结构，意为“不是因为，而是因为”
Not thatI don't like the film, but thatI have no time for it.不是因为我不喜欢这部电影，而是因为我没时间看。
The soldier's essential honor was not thathe killed his enemy, but thathe was willing to die.军人的真正光荣不是杀敌，而是不惜牺牲。
四、目的状语从句
1、that，so that，in order that引导目的状语从句
目的状语从句由that，so that，in order that等引导。从句中的谓语动词前常有情态动词may、might、can、could、will, would等。
John shut everybody out of the kitchen so that he could prepare his grand surprise for the party.约翰把其他人关在厨房外，目的是能够为晚会烹饪出人意料的东西。
These men risk their lives in order that we may live more safely.这些人甘冒生命危险，是为了让我们活得更安全些。
2、lest, for fear that和in case引导目的状语从句
这三个连词词组的意思是“以防，以免”。lest的从句一般要用虚拟语气，形式是“should+动词原形”或省掉should。for fear that和in case从句一般用虚拟语气，但有时也可以用陈述语气。
I obeyed her lest she should be angry. 我得顺着她，免得她生气。
Take a hat with you in case the sun is very hot. 倘若太阳很利害，你就把帽子戴上。
五、结果状语从句
1、so that，so…that, such…that引导结果状语从句
So difficult did I feel it to live in an English-speaking country thatI determined to learn English well.我感到在讲英语的国家里生活太难了，因此我决定学好英语。
He worked hard so thathe passed the exam. 他学习很努力，结果通过了考试。
He spoke for such a long time thatpeople began to fall asleep.他讲了那么长时间，人们开始打起瞌睡了。
2、so…that与such…that的区别
这两种结构都可引导结果状语从句。so是副词，后接形容词或副词；such是形容词，后接名词。
（1）单数名词
在so...that与such...that中间出现的是单数名词，且该名词前有形容词修饰时，这两种结构可互换，但要注意它们的词序不同:such+ a/an+形容词十名词=so+形容词+a/an+名词。
She is such a good teacher thatall of us love her.= She is so good a teacher thatall of us love her.她是一位很好的老师，我们都敬爱她。
（2）不可数名词或复数可数名词
如果被修饰的是不可数名词或复数可数名词时，一般须用such...that。
He made such rapid progress thatbefore long he began to write articles in English.他进步很快，不久就开始用英语写文章。(不可数名词)
They are such interesting books thatwe all want to read them.这些书是那么有趣以致我们都想读一读。(复数可数名词)
（3）名词前有many，much，little，few修饰时
如果不可数名词或复数可数名词前有many，much，little，few修饰时，则用so…that。
I've had so many falls thatI'm black and blue all over.我摔了好多次跤，周身青一块紫一块的。(复数可数名词)
George had so little money thathe had to get a job.乔治没有钱，所以他不得不找工作干。(不可数名词)
They are such little children thatthey can't do anything.他们是小孩,什么事情都干不了。
教你巧学巧记:
名前such，形、副so，
多多少少也用so。
little属特殊，
“小”用such，“少”用so。
3、如何判断so that引导的目的状语从句与结果状语从句
（1）当表达的含义是“为了”、“以便”时，为目的状语从句；当表达的是“以至于”、“因此”含义时，为结果状语从句。
If you do know, answer in a loud enough voice so that all the class may hear.(目的状语从句)如果你的确知道，应大声回答，以便让全班学生都可以听见。
It rained hard the day before yesterday, so thatshe had to stay at home.(结果状语从句)前天雨下得很大，因此她只好呆在家里。
（2）当从句的谓语动词有情态动词can, could, may, might等时，是目的状语从句；当从句里没有情态动词，且谓语动词是一般现在时（过去时）、现在完成时等时态时，是结果状语从句。
We stopped at Salt Lake City so thatwe could(might)visit the monument to seagulls. (目的状语从句)我们在盐湖城逗留，以便可以参观为海鸥修的纪念碑。
They have walked a long way, so thatwe are all tired. (结果状语从句)他们走了很长的路，所以都很累。
（3）当从句之前的so that可用in order that代替时，是目的状语从句；反之，是结果状语从句。
We now study hard so that we may work well in the future.(=We now study hard in order that we may work well in the future. (目的状语从句)我们现在努力学习是为了将来更好地工作。
(4)当so that之前有逗号时，是结果状语从句；反之，是目的状语从句
The story is very interesting, so thatI like it very much.(结果状语从句)这部小说很有趣，因而我非常喜欢。
六、比较状语从句
比较状语从句一般由as…as(和一样)，not as/so…as(与……不一样)，than(比),the more…, the more…(越……越……)引导。
The director gave me a better offer than he gave Dick.导师给我的提议比给狄克的好。
In recent years travel companies have succeeded in selling us the idea that the furtherwe go, the betterour holiday will be.近几年旅游公司已成功地对我们公众宣传了去得越远，假日越好的观点。
John plays football as well as,ifnot better than, David. 如果说约翰的足球踢的不比大卫好，至少和他踢的一样好。
I can't run as/so fast as he can. 我不能跑得他那样快。
七、让步状语从句
让步状语从句由though，although，as，even if (though)，however，whatever，whoever，whenever，no matter +wh词，等引导。
1、even if, even though, although，though引导的让步状语从句
这四个词（词组）都有“虽然、即使、尽管”的意思。even if和even though带有较强的意味，语气比although和though强。though比although通俗，但不如although正式,都不能和but连用，但可以和yet, still或nevertheless连用。可以放在主句前面也可以放在主句后面。even if，even though所接的句子常用虚拟语气。
We wouldn't give up even if we should fail ten times.即使是我们失败十次，我们也不会放弃。
He might have given you more help，even though he was very busy．尽管他很忙，他可能给了你更多的帮助。
2、as或though引导让步状语从句
（1）由as或though引导让步状语从句用倒装语序
Proud as these nobles are, he is afraid to see me.这些贵族尽管很傲慢，他们却害怕见我。
（2）如果表语为单数可数名词，这个名词不带冠词
12-year-old girl as she is, she has had a good command of English.她虽然只是个12岁的女孩，但是她已经熟知英语。
Child as he is，he knows a lot.虽然他还是个孩子，却懂的很多。
(3)如果句中谓语包含情态动词或助动词，则将实意动词放在as之前
Try as I might，I couldn't lift the stone.我使多大劲儿也搬不动这块石头。
Praised as he was, he remained modest.他虽然受到表扬，但仍然保持着谦虚。
（4）如果句中谓语仅有实意动词，则将实意动词(原形)放在as之前，并在主语后面加助动词do, does, did或will。
Torture her as they did, the enemy got nothing out of her.虽然敌人拷打她，却没有能从她嘴里得到什么。
Fail as he did, he would never give up.尽管他失败了，但他决不会放弃。
注:但是，如果在这种情况下，句中谓语有副词修饰，则将副词放在as之前。
Again and again as he failed, he didn't lose heart.他虽然多次失败，但仍不灰心丧气。
Much as I admire his courage, I don't think he acted wisely.我虽然佩服他的勇气，但是我认为他这样做是不明智的。
3、由no matter+ wh词和由疑问词＋ever引导让步状语从句
由no matter引导，表示“不管；无论”；由疑问词＋ever引导，表示“不管，不论”。这类词有：whatever，whichever，whoever，however， whenever，wherever等,他们相当于no matter+ what（which，who，how，when， where），都不能与but，so，and等并列连词同时使用。
We'll have to finish the job, however(no matter how) long it takes. 不管需要多长时间，我们都一定完成这项工作。
No matter what(Whatever) you do, don't tell him that I told you this. 无论你做什么，别告诉他我对你说过这件事。
4、由whether．．．or引导让步状语从句
由whether．．．or引导让步状语从句表示“不论……还是”，提供两种对比的情况。
I 
shall go, whether you come with me or stay at home. 不论你来还是留在家中，我都要去。
Whether we like a particular piece of news or not, all we have to do is sit in front of the tube and “let it happen”.不管我们喜欢不喜欢一条消息,我们所能做的只是坐在电视机前，“让它过去”。
八、条件状语从句
条件状语从句可以位于主句前面或后面。
1、 由if，unless引导
if 表示正面的条件，意为“如果”；unless表示反面的条件，意为“除非，如果不”（if not）
You will be late unless you leave immediately.除非你立即走，否则，你会迟到。
If you don't hurry up, you'll be late. 如果你不快点，你就会晚了。
We'll go there unless it rains. 如果不下雨，我们就去那儿。
2、由suppose，supposing，as/so long as， providing, provided, on condition that和in case等引导
这类连词（词组）意思相近，有：“如果、假设、即使、在……条件下”等意义。
Suppose (Supposing) he is ill, what shall we do? 如果他病了，我们该怎么办？
You'll do all right, as long as you follow his advice.只要你听从他的劝告，你就会干得很好的。
In case John comes, please tell him to wait.假如约翰来了，请让他稍候。
You may keep the book a further 
week provided (that) no one else requires it.倘若这本书没有其他人想借的话，你可以再续借一个礼拜。
方式状语从句一般由as(正如；按照)，as if/as though(好像),the way等引导。
1、as 和just as引导方式状语从句
这两个连词的意思是“如…，犹如…，正如…”（in the same manner that）。just as 比as的强调性更强。
You must do everything as I do.你们要照我这样去做。
Just as the water is the most important of liquids, air is the most important gases.正如水是液体中最重要的一种一样，空气是气体中最重要的一种。
2、as if 和as though引导方式状语从句
as if 和as though意为“好像、仿佛”可以用虚拟语气表示不符合事实或与事实相反的情况；也可以用陈述语气表示符合事实的情况。
He walked slowly as if he had hurt his leg. 他慢慢地走，她像腿受伤的样子。
He spoke as if he knew the question very well.他说得好像对这个问题知道得很清楚。
3、the way引导方式状语从句
the way它的作用相当于the manner，后面的引导词常用that引导方式状语，而且经常省略。此时，一般不用in which引导。
I don’t like the way you speak to her.我不喜欢你和她说话的方式。
We didn't like the way that he treated us.我不喜欢他对待我们的方式。
