初二 英语 从句 请详细解答,谢谢! (17 14:44:8)

什么叫条件状语从句？

概念

在复合句中，由从句表示的状语叫做状语从句。它可以用来修饰主语中的动词.形容词.副词等。根据它表达的意思，状语从句可以分为时间状语从句.
状语从句，条件状语从句，比较状语从句，目的状语从句，结果状语从句和让步状语从句等。由连接词if引导的状语从句叫做条件状语从句。（注意：在含有条件状语从句的复合句中，如果主句是一般将来时态，从句要用一般现在时[主将从现原则])

语法

经典语句：If it dosen't rain tomorrow,we will go to the zoo.
If you open the door，i will come in.
条件状语从句就是用以表示“在某种条件下,会……”
常用if ,in case , on condition等词来引导
连接词主要有 if, unless, as/so long as, on condition that,provided,suppose,supposing 等。.
主句用一般将来时，if或unless引导的条件状语从句用一般现在时。
固定搭配：unless = if...not.
e.g. 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.
if 引导的条件句有真实条件句和非真实条件句两种:
真实条件句，
如：If it rains tomorrow, we won’t go on a picnic.
非真实条件句是虚拟语气的一种，表示与事实相反，如：
If I were you, I would go with him.
if wrless,on condition that
so/as long as只要
由as (so) long as, in case引导。
So long as you’re happy, it doesn’t matter what you do.
只要你高兴，你做什么都没有关系。
You may borrow my book as long as you keep it clean.
只要你保持书的清洁，你就可以把我的书借去。
Take your umbrella in case it rains.
带着你的伞吧，以防下雨。

以if 引导的从句

条件状语从句 条件状语从句就是用以表示“假设条件下会。。。” 常用if ,in case , on condition等词来引导 条件状语从句分真实条件句和非真实条件句 真实条件句， 如：If it rains tomorrow, we won”t go on a picnic. 非真实条件句是虚拟语气的一种，表示与事实相反，如： If I were you, I would go with him.

条件状语从句 条件状语从句：表示条件或要求性质的状语从句 例句： 1）I can lend you the bike on condition that you return it on time我可以把自行车借给你，但条件是你必须限期归还(on condition that you return it on time是条件状语从句) 2）You'll fail if you don't work hard如果你不努力就会失败(if you don't work hard是条件状语从句) 引导词有：if,unless,so(as)long as,on condition that(只要）等 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 tied, let's go...条件状语从句 条件状语从句：表示条件或要求性质的状语从句 例句： 1）I can lend you the bike on condition that you return it on time我可以把自行车借给你，但条件是你必须限期归还(on condition that you return it on time是条件状语从句) 2）You'll fail if you don't work hard如果你不努力就会失败(if you don't work hard是条件状语从句) 引导词有：if,unless,so(as)long as,on condition that(只要）等 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 tied, let's go out for a walk. 典型例题 You will be late ___ you leave immediately. A. unless B. until C. if D. or 答案A。 句意：除非你立即走，否则你就回迟到的。可转化为 If you dong leave immediately, you will be late. B、D句意不对，or表转折，句子如为 You leave immediately or you will be late. 引导条件状语从句最常用的连词是if,由if引导的条件状语从句表示在某种条件下某事很可能发生。如: If you ask him, he will help you.如果你请他帮忙,他会帮你的。 If you fail in the exam, you will let him down.如果你考试不及格,你会让他失望的。 另外,if从句还表示不可实现的条件或根本不可能存在的条件,也就是一种虚拟的条件或假设,从句多用一般过去时或过去完成时。如: If I were you, I would invite him to the party.如果我是你,我会邀请他参加聚会。 I would have arrived much earlier if I had not been caught in the traffic.如果没有堵车,我会到的早一点儿。 那么,除了if之外,是否还有其他连词也可以引导条件状语从句呢?回答是肯定的,不仅有,还有很多。这些词由于出现的频率较小,且用法较复杂一些,所以不如if为大家所熟知罢了。下面就这些词的用法以例句的形式进行一下简单总结。 1. unless conj.除非,若不,除非在……的时候 You will fail to arrive there in time unless you start earlier.如果你不早点动身,你就不能及时赶到那儿。 Unless it rains, the game will be played.除非下雨,比赛将照常进行。 2. on condition(that)...在……条件下,如果 on condition (that)...引导的条件从句是主句事件发生的前提条件或唯一条件。 I can tell you the truth on condition that you promise to keep a secret.我可以告诉你真相,条件是你答应保守秘密。 You can go swimming on condition (that) you don't go too far from the river bank.你只有在不远离河岸的条件下才可以下水游泳。 3. supposing conj.如果,假如 supposing引导的条件从句表示一种假设条件。 Supposing it rains, shall we continue the sports meeting?倘若下雨,我们的运动会还要继续举行吗? Supposing something should go wrong, what would you do then?假如出了什么问题,你准备怎么对付? 4. provided conj.假如,除非,以……为条件 provided (that) +从句表示一种假设条件。 He will sign the contract provided we offer more favorable terms.如果我们提出更优惠的条件,他就会在合同上签字。 He won't be against us in the meeting provided that we ask for his advice in advance.如果我们提前征求一下他的意见,他就不会在会上反对我们。 从上述例句可以看出if, unless, on condition (that), supposing, provided等词引导的条件状语从句,主从句条件关系分明,结构清晰。但有些句子,虽没有含条件关系的连词,却也隐含着条件关系,这些句子常用一些词,如but for, without等引出一个介词结构来表示条件,条件常常是虚拟的,或与事实相反的假设。如: but for若非,要不是 But for the rain, we should have a pleasant journey.要不是下雨,我们的旅行肯定会很愉快。 But for your help,we should not have finished in time.要不是你帮忙,我们肯定不能及时完成任务。 1）表语从句 1.定义：用作表语的从句叫做表语从句。 2.构成：关联词+简单句 3.引导表语从句的关联词的种类： （1）从属连词that.如： The trouble is that I have lost his address.麻烦是我把他的地址丢了。 （2）从属连词whether，as，as if.如： He looked just as he had looked ten years before.他看起来还与十年前一样。 The question is whether they will be able to help us.问题是他们是否能帮我们。 注：从属连词if一般不用来引导表语从句，但as if却可引导表语从句，如： All this was over twenty years ago，but it’s as if it was only yesterday. 这都是20多年前的事了，但宛如昨天一样。 能跟表语从句的谓语动词一般为系动词be，seem，look等。如： It looked as if it was going to rain.看起来天要下雨了。 （3）连接代词who，whom，whose，what，which，whoever，whatever，whichever 连接副词 where，when，how，why. 如：The problem is who we can get to replace her.问题是我们能找到谁去替换她呢。 The question is how he did it.问题是他是如何做此事的。 That was what she did this morning on reaching the attic.那就是她今晨上了阁楼干的。 解释： 1.连词because可引导表语从句。如： I think it is because you are doing too much.我想这是因为你做得太多。 2.在一些表示“建议、劝说、命令”的名词后面的表语从句中，谓语动词用虚拟语气。should+动词原形表示，should可省略。如： My suggestion is that we （should）start early tomorrow.我的建议是我们明天一早就出发。 2）主语从句 1.定义：用作主语的从句叫做主语从句。 2.构成：关联词+简单句 3.引导主语从句的关联词有三类： （1）从属连词that.如：That they were in truth sisters was clear from the facial resemblance between them. 很明显，她们确是亲姐妹，她们的脸型很相似。 （2）从属连词whether.如： Whether he’ll come here isn’t clear.他是否会来这里还不清楚。 （3）连接代词who，whom，whose，what，which，whoever，whatever，whichever 连接副词 where，when，how，why.如： What she did is not yet known.她干了什么尚不清楚。 How this happened is not clear to anyone.这事怎样发生的，谁也不清楚。 Whoever comes is welcome.不论谁来都欢迎。 Wherever you are is my home —— my only home.你所在的任何地方就是我的家——我唯一的家。 解释： 1.主语从句能用it作形式上的主语。常以it作形式主语的句型有： A.It+be+形容词（obvious，true，natural，surprising，good，wonderful，funny，possible，likely，certain，probable，etc.）+that从句。如： It is certain that she will do well in her exam.毫无疑问她考试成绩会很好。 It is probable that he told her everything.很可能他把一切都告诉她了。 B.It+be+名词词组（no wonder，an honor，a good thing，a pity，no surprise，etc.）+that从句。如： It’s a pity that we can’t go.很遗憾我们不能去。 It’s no surprise that our team should have won the game.我们没赢这场比赛真意外。 C.It+be+过去分词（said，reported，thought，expected，decided，announced，arranged，etc.）+that从句。如： It is said that Mr.Green has arrived in Beijing.据说格林先生已经到了北京。 It is reported that China has sent another man-made earth satellite into orbit. 据报道中国又成功地发射了一颗人造地球卫星。 D.It+seem，happen等不及物动词及短语+that从句。如： It seems that Alice is not coming to the party at all.Alice似乎不来参加晚会。 It happened that I was out that day.碰巧我那天外出了。 E.It+doesn’t matter（makes no difference，etc.）+连接代词或连接副词引起的主语从句。如： It doesn’t matter whether she will come or not.她是否来这无关紧要。 It makes no difference where we shall have the meeting.我们在哪里开会毫无区别。 F.当that引导的主语从句出现在疑问句中时，要以it作形式主语，而把主语从句后置。如： Is it true that the scientist will give us a lecture next week？ 下周那位科学家将给我们作报告是真的吗？ Does it matter much that they will not come tomorrow？ 他们明天不来很要紧吗？ G.当主语从句出现在感叹句中时，要以it作形式主语，而把主语从句后置。如： How strange it is that the children are so quiet！ 孩子们这么安静真奇怪！ 2.注意连接代词whoever，whatever，whichever等引导主语从句的含义。 Whoever comes will be welcome.（whoever=the person who）来的人将受到欢迎。 Whatever he did was right.（whatever=the thing that）他所做的事情是正确的。 Whichever of you comes in will receive a prize.（whichever=anyone of you who）你们当中不论哪个进来将会得到奖 3）宾语从句 1.定义：用作宾语的从句叫宾语从句。 2.构成：关联词+简单句。 3.引导宾语从句的关联词有三类： （1）从属连词that.如： He told us that he felt ill.他对我们说他感到不舒服。 I know he has returned.我知道他已经回来了。 注： that在引导宾语从句时也并不是任何情况下都可以省略。在以下情况下，that不能省略。 1.Everybody could see what happened and that Tom was frightened.（and连接两个宾语从句，that宾语从句放在and的后面时，that不能省略。） 大家都会看出所发生的事情并知道Tom非常害怕。 2.I know nothing about him except that he is from the south.（that引导的宾语从句作介词宾语时，that不能省略。） 对他我一无所知，只知道他是南方人。 3.That he ever said such a thing I simply don’t believe.（that从句位于句首时，that不可省略