“条件”表达法是中学英语中相当重要的语言现象，也是高考测试的重点和难点，为使同学们更好的复习和运用，减少失误，现就其相关知识与考点作如下归纳分析：
条件即一个动作或一种情况发生存在的前提，有真实条件和非真实之分。简述如下：
一 从句
常用来引导条件从句的连词有：if，unless，even if ，in case ，as long as，so long as，so far as ，
On condition that，
1 考查in case 引导条件句的用法
[NMET2000] I don’t think I’ll need any money but I ‘ll bring some_____.
A at last B in case C once again D in time
【解析】本题考查in case 引导条件句的用法,答案为: B ..in case引导条件句,其意为“假使；以防（万一）”。其位置较为灵活，可置于句首或句尾 。其时态常用一般现在时表示将来，但也可用“should﹢动词原形”。
例如：Be quiet in case you should wake the baby
【测试演练】（2000春季京皖卷）(答案: C)
John may phone tonight。I don’t want to go out____he phones.
A as long as B in order that C in case D so that
2考查if 引导条件句的用法
[NMET2000] The WTO can’t live up to its name____ it does not include a country that is home to one fifth of mankind
A as long as B while C if D even though
【解析】本题考查If 引导条件句的用法,答案为: C. 在if 引导的条件句中,应注意 时态的对应性,一般来说,if引导的条件句常用一般现在时或现在完成时表示将来而主句常用一般将来时,祈使句或情态动词的一般式.
【测试演练】(MET1992) (A)
If city noises ___ from increasing, people ____ shouted to be heard even at the dinner table
20 years from now .
A are not kept ;will have to B are not kept ; have to
C do not keep ;will have to D do not keep; have to
3 考查unless 引导条件句的用法
[NMET1992] You will be late ___you leave immediately.
A unless B until C if D or
【解析】答案：A 。unless 引导的从句，意义为“除非，如果不”相当于“if….not”
4考查if 引导省略条件句的用法
[上海高考卷1998] If ____the same attention again, he is sure to get well
A giving B give C given D being given
【解析】答案：C .在条件状语从句中,如果从句的主语与主句的主语一致,且从句中有系动词be,可以将从句主语及be 省去,构成省略.
5考查if省略的条件句的用法
[上海高考卷1994] it rain tomorrow ,we would have to put off the visit to the Yangpu Bridge
A Were B Should C Would D Will
【解析】答案：B .本题属于虚拟语气倒装形式.若省略if可将were,( had ,should )提到句首
变为倒装形式。
If I were at school again，I would study harder
→Were I at school again，I would study harder
If you had come earlier，you would catch the bus。
→Had you come earlier，you would catch the bus。
【易错点解析】若省略的条件句中的谓语动词是否定形式时，不能用动词缩写形式。
误：Weren’t it for the expense ,I would go abroad now
正;Were it not for the expense ,I would go abroad now
二 分句
1考查“祈使句﹢and / or/or else / otherwise﹢简单句”祈使句表示条件,简单句表示结果，但表达的意义比if 从句更为紧迫。
[NMET1998]_____it with me and I’ll see what I can do
A when left B leaving C if you leave D leave
【解析】答案：D ,
【测试演练】(上海高考卷1998)
One more week, ____we will accomplish the task
A or B so that C and D if
【解析】答案：C.
2 由转折连词引导的分句表示虚拟条件
I was very busy today。Otherwise（＝if I had not been very busy that day），
I would have taken part in the discussion 今天我很忙，否则，我会参加那次议论的
He would have given you more help，but he was busy。
3 有些谚语中的省略句虽没有表示条件的连词，也可表示条件。
Easy come， easy go .(＝If money comes easily, it will go easily)
First come, first served (＝If one comes first ,he will be served first)
三 名词词组
其作用相当于条件状语从句
One step further, and you are lost.(＝If you take one step further,you will be lost)
Another sound from me, and the snake might strike .
四 介词短语
其作用相当于条件状语从句.常用的介词有: with, without, but for
We couldn’t have succeeded without your help(＝If you hadn’t helped us, we couldn’t have succeeded )如果没有你的帮助,我们就不会成功.
五 不定式短语
其作用相当于条件状语从句.
To look at him (＝If you were to look at him), you would consider him a young man
六 独立主格结构
其作用相当于条件状语从句.
Weather permitting, we will have an outing tomorrow
All things considered ,her paper is of greater value than yours
七 动词转化为连词
save that(只是) ,providing（that），provided that，suppose（supposing）,considering(考虑到,鉴于) given ,seeing that等等。
I agree with you ,save that you have got something wrong
八 含蓄条件句
有时为了表达的需要,通过其他手段来代替条件句
I was ill that day .otherwise I would have taken part in the sports meet(副词)
He telephoned to inform me of your birthday. Or I would have known nothing about it(连词)
A man who stopped drinking water would be dead in about seven days(定语从句)
条件状语从句的紧缩形式
Come tomorrow if possible可能的话就明天来吧
If so , you must fetch it as soon as possible如果是那样,你必须尽快去拿来.
I will buy a TV set if necessary
He has no money .if any, he will give m
