作者:城市网 来源:城市网学院 更新日期：2013-3-6
假设法句型
If + Present Tense …， S + will/shall + V …
结构︰If+现在式…，S+未来式…
说明︰if 子句用现在式，表示须具备的条件，主句用未来式表示可能的结果，整句含意为“如果…，那麽…”。will 用於所有的人称，在 I 和 we 之後可用 shall 代替 will。若主句的主词为 I 或 we 时，可以用 shall 代替 will。像 if necessary（如果需要），if possible（如果可能），if so（如果这样）等固定片语实际上是省略了的 if 子句。
If I lose my job, I will/shall go abroad. 如果我失业了，我就出国。
If I have a headache, I will take an aspirin. 如果我头痛，我就服一片阿斯匹林。
If it rains, we will stay at home. 如果下雨，我们将待在家里。
If the weather clears, we'll go for a walk. 如果天晴，我们就去散步。
If the weather doesn't clear, we won't go for a walk. 如果天不晴，我们就不去散步。
Inflation may be rising, if （it is） so, prices will go up.
通货膨胀率可能上升。如果是这样，物价就会上涨。
If possible, She wants to go with us. 可能的话，她想跟我们一起去。
Sterling may fall, if （this should be） so, interest rates will rise.
英国货币可能贬值，如果果真如此，利率就会上升。
If + Present Tense …， S + Modal Verb …
结构︰If + 现在式，主词+情态助动词
说明︰本句型实为句型之变体。之所以用情态助动词，主要是因为说话者对可能的结果不是太肯定或者是想表达例如必要的意思。
If it is fine tomorrow, we can go out. 如果明天天气好，我门可以出门。
If it is fine tomorrow, we could go out. 如果明天天气好，我门能够出门。
If it is fine tomorrow, we may go out. 如果明天天气好，我门可能出门。
If it is fine tomorrow, we might go out. 如果明天天气好，我门可能出门。
If it is fine tomorrow, we should go out. 如果明天天气好，我门宜於出门。
If it is fine tomorrow, we ought to go out. 如果明天天气好，我门宜於出门。
If it is fine tomorrow, we must go out. 如果明天天气好，我门必须出门。
If I should …， Imperative Sentence.
结构︰If I+should …+祈使语气
说明︰代替，增加了条件的不确定性。本句型常用在想礼貌地提出要求或建议，或者想圆通地告诉他人该做什麽事的场合。用 should 起始句子即可不用 if 而表示条件。这种用法比较正式，常用於诸如公函之中，而不用於日常会话。
If you should see him, please give him my regards. 如果你见到他，请代我向他致意。
Should you see him, please give him my regards. 如果你见到他，请代我向他致意。
If you should happen to see him, please give him my regards.
如果你万一见到他，请代我向他致意。
Should you happen to see him, please give him my regards.
如果你万一见到他，请代我向他致意。
If you should write to her, send her my love. 如果你给她写信，请代我向她问候。
Should you not wish our agent to call, please let us know.
你若不希望我们的代理人去造访，请告之。
Should you be interested in our offer, please contact us.
你若对我们的报价感兴趣，请与我们联系。
If I should …， I will …
结构︰If…should…，…would（will）/should（shall）等+原形动词
说明︰这是表示与未来事实相反的假设<句型>，if <子句>要用<助动词> should，译成“万一”。should可置於<主词>前，将 if 省略。<主要子句>的<助动词>则视可能性做变化：若可能性低，则为过去式，若可能性高，则为现在式。should 可以提前，而将 if 省略。
If he should #e, I would tell him the truth. 万一他来，我会把真相告诉他。
If he should #e, I will tell him the truth. 万一他来，我一定会把真相告诉他。
Should the boy #e again, I would throw him out. 要是那男孩在来，我就把他撵出去。
If it should rain, our plan would be spoiled. 万一下雨，我们的计划就泡汤了。
Should that be true, the contract would be canceled. 假如那是真的，合约就该取消。
Should another world war break out, what would be#e of human beings?
万一另一次世界大战爆发，人类将会发生什麽事？
If I were to …， I …
结构︰If…were to…，…would/should 等+原形动词
说明︰这也是表示与未来状况相反的假设<句型>，与“if … should, …”大致相同，但“if … were to”所表示的可能性更低，通常用以表示“与真理相反”的<假设语气>。
If the sun were to rise in the west, he would pass the exam.
要是太阳从西边出来，他就会通过考试--他不可能通过考试。
If I were to be born again, I would like to be a bird. 我要是再活一次，我想当一只鸟。
If the sun were to disappear, what would the earth be like?
万一太阳消失了，地球会变成什麽样子？
Were I to die tomorrow, what would my children do?
万一明天我死了，我的孩子们将怎麽办呢？
If I + V-ed, I would …
结构︰If…+过去式动词…，主词+过去式助动词（would/should 等）+原形动词
说明︰这是与现在事实相反的假设句型。if <子句>中的<动词>，不论<主词>为第几人称，一律用 were，were 可置於主词前面，而省略 if。过去式<助动词>除用 should（用於第一人称）、 would（用於第二、三人称）外，还可用不分人称的 could，might 和 ought to，它们与<动词>原形结合起来构成<假设语气>。
If I knew his address, I could write to him. 如果我知道他的住址，我会写信给他。
If I were free now, I might call on him. 如果我有时间，我可能会去看他。
If you were in my shoes （=Were you in my shoes）， what would you do?
如果你站在我的立场，你会怎麽做？
Were I rich enough, I would buy a sports car. 如果我有足够的钱，我就买一辆赛车了。
How happy I would be if I were a few inches taller! 要是我再高几寸，我会好高兴。
If I had a car, I could take her for a drive. 如果我有车， 我就带她去兜风了。
If I had binoculars, I could see that #et clearly.
如果我有望远镜，我就可以清楚地看见那颗彗星。
It is time that …
结构︰It is（high）time+（that）+主词+过去式动词
说明︰此句型意为“已经到了…的时间了”。过去式<动词>处有时亦使用“should+<动词>原形”。that <子句>也能用 to <不定词>来表示。
It is time he went to bed. 该是他睡觉的时间了。
It is time that you left for the duty. 该你当班了。
It is time that you reflected upon your mistakes. 该是你反省思过的时候了。
It is high time he should #e to our house for dinner.已经到了他该上咱家吃晚饭的时候了。
It is time for somebody to teach you to behave yourself.
该是有人教你应对进退之礼仪的时候了。
If I had V-ed, I would have …
结构︰If…had+过去分词…，主词+would/should 等+have+过去分词
说明︰这是与过去事实相反的假设<句型>。if <子句>要用<过去完成式>，<主要子句>则要用过去式<助动词>（would，should，ought to，might，could）+have+过去<分词>。if <子句>中的 had可置於<主词>前面，而省略 If。
If I had seen him, I would have told him the truth. 如果我当时看见他，我会告诉他实情。
I could have finished the task if I had had more time.
如果当时我能有多一点时间，我就能完成这项任务。
If we had known of your departure, we would have seen you off at the airport.
如果我们事先知道你要离开，我们会到机场送行。
I someone had been with him, he might not have been drowned.
如果有人在他旁边，或许他就不会溺死。
I might have been incredulous had I not been accustomed to such responses.
若非我已经习惯了这样的回答，我可能不敢轻易相信。
Had he not apologize to her, she would not have forgiven him.
她（那时）不会原谅他，若非他道了歉。
Had he not saved me, I might have been drowned. 我可能溺死了，若非他救了我。
Had I proposed to you, would you have married me?
我要是当年向你求婚，你会答应嫁给我吗？
Had you not helped us, we should have canceled this transaction.
假如没有你的帮助，这笔生意早就告吹了。
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