英语语法情态动词.docx

1、英语语法情态动词情态动词也叫语气动词，表示说话人对所说动作的看法，认为它可能、应当、必要等。情态动词不能单独作谓语动词，只能和动词原形一起构成谓语动词。英语里的情态动词主要有：can (could), may (might), must, shall, will, would, need, dare, should, ought to。情态动词在任何主语后没有人称和数的变化。1. can 和could 表示能力Whales cannot live on land. A computer cant think for itself. 计算机不会独立思考。He hurt his foot and

2、couldnt play football. be able to 可用于多种时态，can和could只用于现在时和过去时。He will be able to go with us this afternoon. I havent been able to see the difference yet. 如果表示做到，设法干成了某事，常用be able to 来表达（相当于managed to do sth. 或succeeded in doing sth. ）,而不用can /could。With the firemen, they were able to escape from the

3、 burning house. We were able to get there before the meeting began. 表示可能性can表示可能性时，常用于疑问句和否定句中。Can this be true? Can it be Mr. Black? He cant be at home. 他不可能在家。 He may not be at home. 他可能不在家。can间或可用于肯定句，表示理论上的可能性，表示笼统的时间，事物的特征。Anybody who wants to try can be successful. 只要想试，任何人都可能成功。Scotland can b

4、e very warm in September. 表示许可和请求在日常生活中，can可以代替may, 表示允许；could 可以代替can，但语气较为婉转。Can/Could I use your pen?Yes, of course you can. (不能用could) No. Im afraid not. 习惯短语：cannottoo越越好 You cannot be too careful. cannot but 不得不 I cannot but do so. 我不得不这样做。 can 和could 后面接动词的完成式，表示对过去情况的猜测或判断。can常用于疑问句和否定句，coul

5、d用于肯定句，表示一个非事实的或不可能实现的可能性。Where can he have gone?He cant have gone to school. -Its Sunday. You were stupid to go skiing there. You could have broken your leg. could have done 本来能做而实际未做，表达遗憾的感情色彩-I stayed at a hotel while in New York. -Oh, did you? You could have stayed with Jane. 2. may 和might 表示允许m

6、ight 比may 语气更客气、更委婉You may take a rest now. May/Might I take the book out of the room? No, you mustnt / may not/ cannot.Sure / Certainly/ Of course 否定用于拒绝给予许可，或禁止做某事。通常在官方公告中。Students may not stay out after midnight. 学生午夜后不得在外逗留。 表示可能性常用于肯定句和否定句，指说话人的猜测。might指把握性不大，He may/might come. Youd better sta

7、y here for a moment. I may/might not be back for dinner. (Im not sure whether Ill be back. ）may 强调逻辑上的可能。can 强调事实上的可能。He looks pale. He may be ill.他脸色苍白，可能有病。He is in poor health. He can be ill at any time.他体质很差，任何时候都有可能生病。(3) may/might + have + 过去分词表示对过去的推测，认为过去可能发生的动作。may 比might的把握性更大He may/might

8、have gone abroad. He may/might have had some kind of accident. (4) 用于祈使句，表祝愿May you both be happy！ May you succeed！(5) 习惯用语：may /might as well 还是的好You may as well give him the letter. I might as well stay at home tonight. (6) 在表示目的状语从句中构成谓语Write to her at once so that she may know in time. He died s

9、o that the others might live. 3. must 表示必须、一定（现在和未来）Must I get ready now? We must finish this before he comes. must 和have to：must表示说话人主观认为的必须，而have/has to表示客观的需要，译为不得不I really must stop smoking. （我认为应该戒烟）I have to stop smoking. （客观情况使我戒烟） have to 有时态和人称的变化，而must没有I had to write some letters last nig

10、ht. I will have to meet Mr. Edward at three oclock this afternoon. must not=mustnt表示“禁止”， do not have to =dont have to 表示 不必You mustnt go now. You dont have to go now. Must I hand in my paper now?Yes, you must. (No, you neednt. / No, you dont have to. ) 表示判断推测暗含很大的可能性， must仅用于肯定句，不能用于疑问句和否定句。They mu

11、st be in the classroom now. You must be ill. You look so pale. must + have + 过去分词表示对过去事情的推测。They must have heard the news. Something must have happened. The ground is wet. It must have rained last night. must用在反意疑问句中He must work hard at English, mustnt he ?You must renew the book, neednt you?He must

12、 be a teacher, isnt he ? （不说mustnt）You must have studied English for many years, havent you? （不说mustnt）He must have arrived here yesterday, didnt he? （不说havent） must表示偏偏The car must break down just when we were about to start off. 我们正要出发时偏偏车又坏了。4. will 和would 表意愿、决心 在陈述句或在条件状语从句中。 I will never do it

13、 again. I will finish my lesson even if I have to stay up all night. 即使我整夜不睡觉我也一定要把功课做完。If you will allow me, Ill go with you. 如果你愿意的话，我将跟你去。 would 可表示过去的习惯动作He would sit there for hours sometimes, doing nothing at all. Every morning I would go for a long walk. 表示询问对方的意愿或向对方提出请求, would比will 的语气更婉转Wi

14、ll you please pass me the magazine? Sure / Certainly。Wont you come over? 请到这边来好吗？ will 可以表示现在或当前的习惯性、经常性、倾向性。常译成 惯于、总是Oil will float on water. 油浮在水面上。No matter what you say, he will always argue with you. 不管你说什么，他总是和你争论。A wise man changes his mind, a fool never will. 聪明人能随机应变，傻瓜是不会的。Water will boil

15、at 100. 水在摄氏100度时总是要沸腾的。The door wont shut. (6) 表示可能表示说话人对将来和现在的预测。对现在的预测认为肯定会发生。I think he will be all right now. 我想他现在一定好了。That would be his mother. 那肯定是他母亲。5. shall 用于第一、第三人称疑问句，表示说话人征询对方意见或请求指示Where shall I put my bag?Shall he come in or wait outside? 用于第二、第三人称，表示意愿、期望、允诺、命令、强制、警告、威胁等语气。You shal

16、l keep your room in order. （表命令）He shall be sorry for it one day, I tell you. （表警告）He shall get his money if he tells the truth. (表允诺) No one shall stop me. 不许任何人阻止我。（表意志和决心）shall在条约，规章和法令等文件中，表示义务和规定。Each player shall wear a number. 每个运动员必须带上号。The new regulation shall take effect on Oct. 1st. 新章程十月

17、一实施。(3) 表示说话人的猜测，估计应该I shall be rich one day. 总有天我会发财的。That should be Janet coming upstairs now. 正在上楼的准是珍妮特。6. should表示责任、义务、建议、劝告，用于各人称。You shouldnt judge a man always by the clothes. 你不应该总是以貌取人。You should always think of others before yourself. （表劝告）表推测、可能，暗含很大的可能。I think he should be home now. Yo

18、u should know his address. should / ought to + have + 过去分词表过去本应完成而未完成的动作shouldnt / oughtnt to + have + 过去分词表示过去发生了不应发生的动作He should have arrived by this time. （其实未到）You shouldnt have made so much noise. （事实是吵了） 用在why , how开头的疑问句中或that 引导的从句中。表达说话人意外和不满，竟，竟会Why should you be so late? 为什么你竟这么晚？How shou

19、ld I know? 我怎么会知道？Im sorry that you should think so badly of me. 你竟把我想得那么坏，我感到遗憾。(5) 用在if 引导的条件状语从句中，表示“万一”。Ask her to ring me up if you should see her.If you should change your mind, please let me know.(6) 用于建议、命令、要求等的从句中，构成虚拟语气We demanded that our wages should be raised. It is suggested that he sh

20、ould go there by air. My suggestion is that we should send a few people to help them. 7. need 和dare need 作情态动词，表示需要，用于否定句和疑问句中，无人称和数的变化。We neednt go there tomorrow. Need I tell you all the details? dare作情态动词，通常用在否定句和疑问句中，无人称和数的变化。He dare not do so. I dare not stand on the chair. How dare you say suc

21、h a thing? 你怎么敢说这种话？ need 和dare 也可作行为动词，与一般动词的变化相同。Do I need to tell you all the details?It needs to be done at once. You dont need to worry about that. dare在否定句中有时带to, 有时不带to。He did not dare (to ) do so. 习惯用语：I dare say表示 我想、大概。Theres something wrong with the radio, I dare say. I daresay you are ri

22、ght. neednt + have +过去分词表示过去本来不必做某事而实际上做了，本不必做You neednt have come. (=You didnt have to come. ) （事实上你来了）He neednt have waited for me. （=He didnt have to wait for me. ） (事实上他等我了)表示推测的情态动词用法归纳：肯定句； 对当前行为、情况或状态的推测：must /may /might /could + do/be 语气的肯定程度依次递减。其中，might 和could并非过去时态，只是语气较为委婉或可能性较小He must/m

23、ay/might/could be in the reading room. 他肯定/可能/也许在阅览室里。I must look funny in this hat. 我戴这顶帽子看起来一定很滑稽。 对此时此刻正在进行的动作的推测：must /may/ might/ could + be + doingHe must /may/ might/ could be watching TV at this time. 他此时一定/可能/或许在看电视。They must be waiting for us. 对过去发生的事情的推测：must /may /might /could + have +过去

24、分词They must have arrived by now. You look very tired. You must have stayed up last night. You may have read about it in the papers. 过去的一段时间内一直在进行的动作：must/may /might/ could + have + been +doingThey are sweating all over. They must have been working in the fields. 他们浑身是汗，准是在地里劳动来着。He may have been wai

25、ting for us for an hour. 他可能等我们一小时了。否定句：can/could not不可能，想必不会 may/might not可能不 对当前行为、情况或状态的推测：He may not be busy now. 也许他现在不忙。He can not be busy now. 他现在一定不忙。He cant be in the reading room. I saw him on the playground just now. 他不可能在阅览室里，我刚看到他在操场上。 对此时此刻正在进行的动作的推测：They cant be telling the truth. 他们不

26、可能在说真话。They may not be telling the truth. 他们可能没在说真话。 对过去发生的事情的推测：He cant have finished the work so soon. 这项工作他不可能完成得这样快。He may not have achieved all his aims. But his effort is a good one. 他可能没达到他的全部目的，但他还是认真做了努力的。 过去的一段时间内一直在进行的动作：He cant have been waiting for us so long. 他不可能等我们那么长时间。疑问句中：常用can/co

27、uld来表示说话人的猜疑、怀疑或不肯定的语气Where can he be now? 他现在会在哪里呢？Can it be true? 那会是真的吗？Its so late. Can Tom be reading? 这么晚了，汤姆还在看书吗？What can he be doing? 他可能在做什么呢？Can she have told a lie? 她会不会说谎了？Where can she have gone? 她会上哪儿去了呢？Multiple choice1. We have plenty of time. We _ run so fast. A. mustnt B. neednt C

28、. have to D. must2. Where _ my sister wait for you? In the classroom?A. need B. shall C. may D. can3. _ you please tell me the way to the library?A. Would B. ShouldC. Must D. Need4. He didnt go to the library last Sunday, or I _ him. A. would see B. could meet C. might have seenD. might see5. -Do yo

29、u have to leave now? -Im sorry, but I really_. A. cant B. have C. should D. must6. The classroom is empty. They _ be reading there now. A. mustnt B. cant C. must D. should7. -Remember to attend the meeting. -I _. A. do B. will C. cant D. would8. -I was waiting for you this time yesterday. -Sorry, I

30、_ you to tell you that I couldnt come. A. must have called B. would have been calling C. could have been calling D. should have called9. We _ not to make so much noise in the lab. A. need B. dare C. can D. ought10. You _ have come here yesterday, _ you?A. mustnt , did B. couldnt, has C. must, havent D. must, didnt11. Whenever I was not at home, my child _watch TV. A. will B. would C. were toD. were going