亲爱的同学们，条件状语从句是大学英语四、六级考试中考得非常多的语法项目，所以理解和掌握条件状语从句至关重要。条件状语从句分为真实条件句和非真实条件句，非真实条件句将在虚拟语气中讲解，在这里我们主要讲解真实条件句。
18.1条件状语从句的基本用法
引导条件状语从句的连接词有if， unless， as long as， so long as， providing that， provided that，suppose that， supposing that， in case， only if， if only， on the condition that 等。
1.if
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。例如：
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。
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。
例如：
If I were you， I would certainly have not done such a silly thing.
如果我是你，我肯定不会做那样的蠢事。
2.unless
unless 为连词，意为“除非”、“若不”、“除非在……的时候”。例如：
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 you give up that bad habit， I will not marry you.
除非你放弃坏习惯，否则我不跟你结婚。
3.on condition that
on condition (that) ...意为“在……条件下”，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。例如：
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。
4.suppose/supposing that
suppose/supposing 为连词，意为“如果”、“假如”，supposing 引导的条件从句表示一种假设条件。例如：
Suppose/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？
Suppose/Supposing anything should go wrong， what would you do then？
假如出了什么问题，你准备怎么对付？
5.providing/provided that
provided 为连词，意为“假如”、“除非”、“以……为条件”，“provided (that) +从句”表示一种假设条件。例如：
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。
6.as/so long as
as long as 和so long as 均可用于引导条件状语从句，表示“如果”、“只要”。例如：
So long as you are happy， it doesn"t matter what you do.
只要你高兴，你做什么都没关系。
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。
7.“only if” 和 “if only”
only if 和if only 不仅仅是词序的颠倒，意义也有很大的不同。
（1）only if 引导的从句用陈述语气，意为“只要……”。例如：
Only if we keep up with it， we will necessarily be successful.
只要我们坚持，我们必然会成功。
（2）if only引导的从句要用虚拟语气，可以不要主句，意为“但愿……”、“要是……就好了”。例如：
If only I had understood that question， I would not have asked you.
要是我理解了那个问题，我就不问你了。
Task 1
补全下列句子。
1.________________________________，no one feels like exercising.
除非睡眠充足，否则谁也不想锻炼。
2.________________________________，what shall we do？
如果下雨怎么办？
3.________________________________，please remind me about it.
如果我忘了，请提醒我一下。
4.She did"t mind anything ________________________________.
只要能和吉米在一起她什么也不在意。
5.I"ll come _______________________________.
我可以来，条件是也要邀请艾米。
18.2条件状语从句的相当物
（1）相当于条件状语从句的介词短语。例如：
She is able to protect herself in the event of being attacked.
她能在受攻击的时候保护自己。
There will be no living things without water.
没有水就没有生物。
（2）相当于条件状语从句的不定式短语。例如：
To look at him， you would like him.
要是看到他，你就会喜欢他。
When you are a guest in a western home， it will make you feel more comfortable to know something of foreign customs within the home.
当你在西方人家里作客的时候，如果你知道一些在外国人家中作客的习俗，你会感到更舒适一些。
（3）相当于条件状语从句的分词结构。例如：
Grown in rich soil， these seeds can grow fast.
If these seeds are grown in rich soil， they can grow fast.
如果种在肥沃的土壤里，这些种子能长得很快。
Taking the path that leads out of the town， you will come to a dense wood.
If you take the path that leads out of the town， you will come to a dense wood.
如果你沿着通向郊外的小道前进，就会走到一片密林处。
（4）相当于条件状语从句的被动结构。英语中“主语+被动谓语+by 短语”结构的句子有时还可以表示：如果发生了by 后面的事情，就可能出现前面的情况。例如：
This heart"s desire of all the people could easily have been gained by steadfastness in righteous convictions， and by reasonable.
各国人民的这种衷心热望，如果大家恪守正义的信念，根据常理来处理事情，本来是很容易实现的。
Holding it in her hand， she had suddenly remembered that in the bottom of the box there was a secret compartment which could be opened by sliding the thin wooden base outward.
她手中拿着木匣子，忽然想到匣子下边有一个秘密的夹层，只要把匣底的薄木板抽出，就可以打开。
（5）相当于“祈使句+and/or+简单句”的结构。例如：
Take some hot water and you will feel more comfortable.
If you take some hot water， you will feel more comfortable.
如果你喝些热水，你就会感觉舒服些。
Turn the heat down or your cake will burn.
If you don"t turn the heat down， your cake will burn.
如果你不把温度调低，你的蛋糕会烤焦的。
Check your composition carefully and you will avoid some spelling mistakes.
If you check your composition carefully， you will avoid some spelling mistakes.
如果你仔细检查作文，你就会避免很多拼写方面的错误。
（6）相当于由and 或 or 连接的并列分句。例如：
All you need to do is to dial 114and a computerized voice will give you their phone number.
只要拔114，电脑就会自动给你电话号码。
Attack next Monday or you will be replaced.
下星期一要是不出击，就撤你的职。
（7）相当于条件状语从句的主谓宾结构。在英语中，“主语+谓语+宾语”结构的句子可表示：如果发生这个动作或出现这个状态就会产生后面的结果。例如：
The failure to observe the safety regulation brought an accident of the machine.
如果没有遵守安全规则，机器就出故障。
But the gradual opening of capital accounts must be accompanied by a further strengthening of macroeconomic policies， the development of a system of risk management robust enough to respond to the needs of a more flexible exchange rate and capital account.
如果资本项目逐步开放，必须进一步加强宏观经济政策，大力发展风险管理体制以应对汇率和资本项目频繁波动的需要。
（8）相当于定语从句和一些其他的状语从句。例如：
A nation which stopped working would be dead in a fortnight.
一个国家要是停止运转，不出两周就灭亡了。
“Finally，” she said， “we knew that we could never find peace as long as we were filled with hatred.So we came here to see.”
“最后，”她说，“我们明白了，如果我们心里总是充满了怨恨，就永远也安宁不下来，所以我们就到这里来看看。”
His whistling can be heard even farther away when conditions are favorable - when there is little or no wind.
倘若条件好些--风力很小或根本没风的时候--他发出的哨声还能传得更远。
（9）相当于条件状语从句的其他表达法。例如：
Where there is a will， there is a way.
有志者，事竟成。
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。
He worked very hard， otherwise he might have failed.
他刻苦工作，不然他就失败了。
We could have done better under more favorable conditions.
假设有更有利的条件，我们还会做得更好。
注意：有时假设的情况并不以条件从句表示出来，而是通过一个介词短语来表示，或通过上下文或其他方式表示出来，把条件隐含在句子当中。如以上句中的but for， but that …， in case of， otherwise， supposing， under more favourable condition， without 等表示让步假设状语从句。
Task 2
用条件状语从句的相当物来补全下列句子。
1.， he will be fined.
如果不能及时归还这本书，他就要被罚款。
2.You must be very angry .
没能去那儿，你一定非常生气。
3.， we could do it better.
如果给我们更多的时间，我们可以做得更好。
4._____________________， you must change at Leeds.
如果你往北走，你一定要在利兹市换乘。
5._____________________， I"ll go there on foot.
如果时间允许，我会步行去那儿。
18.3条件状语从句的翻译
（1）条件状语从句译成假设句。例如：
If something has the ability to adjust itself to the environment， we say it has intelligence.
如果某物具有适应环境的能力，我们就说它具有智力。
（2）条件状语从句译成补充句。例如：
We will set out tonight if you are ready.
如果你准备好，我们今晚就可以出发。
Task 3
翻译下列句子。
1.Granted that this is true， what conclusion can you draw？
2.Anybody above the earth will fall unless it is supported by an upward force equal to its weight.
3.Should there be an urgent situation， press the red button to switch off the electricity.
4.Aluminum remained unknown until the 19th century， because nowhere in nature is it found free，owing to its always being combined with elements， most commonly with oxygen， for which it has a strong affinity.
5.The assertion that it was difficult， if not impossible， for a people to enjoy its basic rights unless it was able to determine freely its political status and to ensure freely its economic， social and cultural development was now scarcely contested.
Laughter
Patient： Doctor， I need a liver transplant， a heart transplant， a cornea transplant， a spleen transplant， and a pancreas transplant.
病 人： 医生，我需要做肝脏移植、肾脏移植、心脏移植、角膜移植、脾脏移植和胰腺移植。
Doctor： What makes you think you need all these？
医 生： 你为什么认为你需要做这么多移植手术？
Patient： My boss said if I wanted to keep my job I needed to get reorganized！
病 人： 我的老板说如果我这个人不重新组装的话，就别想保住我的工作！
I.仿照例句改写下列句子。
Example： If you make one more effort， you will succeed.
Make one more effort and you will succeed.
1.If you try some of this juice， perhaps you"ll like it.
2.If you check your composition carefully， you will avoid some spelling mistakes.
3.If you take some hot water， you will feel more comfortable.
4.If you put the documents in a neat file， you will never waste a lot of time finding them.
5.If you do this， you will realize that this moment is all there is， more importantly， this moment is all that you have to make a difference in life.
II.选择题。
1.You will catch a cold put on more clothes.
A.if you
B.if you will not
C.unless you
D.until you
2.If city noises from increasing， people shout to be heard even at the dinner table in 20 years from now.
A.are not kept；will have to
B.are not kept；have to
C.do not deep；will have to
D.do not deep；have to
3.You will be late you leave immediately.
A.unless
B.until
C.if
D.or
4.the English examination I would have gone to the concert last Saturday.
A.In spite of
B.But for
C.Because of
D.As for
5.they invite you to speak， remain silent.
A.If
B.Although
C.Unless
D.Even though
6.If you to the party， you"ll have a great time.
A.will go
B.went
C.go
D.going
7.Provided that you with us， the leader would not criticise you.
A.work
B.will work
C.worked
D.have worked
8.both sides accept the agreement a lasting peace be established in this region.
A.only if， will
B.if only， would
C.should， will
D.Unless， would.
9.You will be late you leave immediately.
A.unless
B.until
C.if
D.or
10.I her the answer if she me.
A.can tell；will ask
B.will tell；will ask
C.would tell；ask
D.will tell；asks
11.there will be a charge in administration.
A.In she wins
B.She wins
C.In the event she wins
D.She wins the event
12.- What are you going to do tomorrow？
- We"ll go to the library tomorrow if it .
A.isn"t rain
B.rain
C.won"t rain
D.doesn"t rain
13.If you to the party， you"ll have a great time.
A.will go
B.went
C.go
D.going
14.It will be a long time Peter his work.
A.since， has finished
B.after， finishes
C.when， will finish
D.before， finishes.
15.I"ll give the book to him if he here next Sunday.
A.will come
B.comes
C.is coming
D.came