1、初高中情态动词专项详解 教师版情态动词分类：情态动词有四类：只做情态动词：must, can(could), may(might), ought to， had better, would rather可做情态动词又可做实义动词：need, dare可做情态动词又可做助动词：shall (should), will(would)具有情态动词特征的实意动词：have (had) to, used to 情态动词的语法特征 1）情态动词不能表示正在发生或已经发生的事情，只表示说话人对有关行为或事物的态度和看法，认为其可能、应该或必要等。 2）情态动词 除ought 和have 外，后面只能接不带t
2、o 的不定式，即：情态动词动词原形 3）情态动词没有人称，数的变化，即情态动词第三人称单数不加-s。 4）情态动词没有非谓语形式，即没有不定式，分词，等形式。 1. can和could的用法A. can 的用法： 表示能力上的“能，会”，可以和be able to的对应时态互换使用 eg: He can speak a little Japanese.他会说一点日语。 Can you speak English? No, I cant (不会，能力上不能). We can be there on time tomorrow. 我们明天能按时去那儿。 If I have a good sleep
3、, I will be able to solve the problem. = If I have a good sleep, I can solve the problem.注意：比较can 和be able to 1）can/ could 表示能力和可能 (过去时用could), 只用于现在式和过去式(could)。 They will be able to tell you the news soon. 他很快就能告诉你消息了。 2）只用be able to a. 位于助动词后。b. 情态动词后。 c. 表示过去某时刻动作时。 d. 用于句首表示条件。 e. 表示成功地做了某事时，只能
4、用was/were able to，不能用could。 He was able to flee Europe before the war broke out. =He managed to flee Europe before the war broke out. 表示请求或允许的“可以” eg: ：Can we go home now, please? No, you cant. （不允许的“不能”）You can only smoke in this room. You cant keep the library books for more than a month. 表示猜测“可能”
5、，与may， might同义；在否定句中，否定形式cant表示推测“不大可能”。 例：Anybody can make mistakes. 每个人都可能犯错。 The news cant be true. 这个消息不可能是真的。与第一、二人称连用时，还可以就可能的解决问题的方式或可能的行为提出建议，也可用could使语气婉转。例：Can / Could we meet again next week? 下周我们可以再见面吗？What shall we do? 我们怎么办呢？ We can / could try asking Lucy for help.我们可以请露茜帮忙试试看。You can
6、 / could help me with the cooking. 你可以帮我做饭。补充知识点：can的其他用法(1)惯用形式“cannot too”表示“无论怎么也不（过分）”。 You cannot be too careful.你越小心越好。 惯用形式“cannot but+ 不定式（不带to）”表示“不得不，只好”。 I cannot but admire her determination.我不得不钦佩你的决心。（2）can not与help, bear, stand等动词连用，表示“禁不住，受不了”。If one had talent, one cant help showing
7、 it.I cant stand waiting any longer.但是cant help but 后面接动词原形，表示“只能”。I can not help but ask you: “do you have loved me?”I cant help but wait.B. could的用法：could作情态动词时，不表示（can的过去）时态 1）表示请求，语气委婉，主要用于疑问句，不可用于肯定句，答语应用can。 Could I come to see you tomorrow? 我明天能来看您吗？ Yes, you can. / No, Im afraid not. / No, y
8、ou cant.Could you please pass me a glass of water? Yes, with pleasure. / No, Im sorry.2）在否定，疑问句中表示推测或怀疑，语气不如can强 He couldnt be a bad man. 他不大可能是坏人。 表示推测时，could不是过去式，只是语气更委婉；若是推测已发生的事或过去的情况，用can/could have done2. 比较may和might 的用法A. may的用法 表示“许可”，用can比较口语化。例：You may / can come if you wish. 如果你想来，你就来。 Y
9、ou may not pick flowers in this park. 本公园内不许摘花。 （may not表示按规定不许可，如果用mustnt则表示说话人不许可。） May I smoke here? 我可以在这里抽烟吗？ No, you mustnt.不行。（mustnt表示明确的禁止。）注意：May I/we？ Yes, you may / can . No, you mustnt. 肯定句中表示推测，“可能” 例：It may rain tomorrow. 明天可能会下雨。 The news may not be true. 这个消息可能不会是真的。 may放在句首，表示祝愿。 M
10、ay God bless you! B. might的用法：1） might 表示推测时，不表示时态。只是可能性比may 小。 He might be at home. 2） 成语： may/might as well，后面接不带to的不定式，意为不妨。 If that is the case, we may as well try. 典型例题: Peter _come with us tonight, but he isnt very sure yet. A. must B. may C. can D. will 答案B. 表可能性只能用may.此句意可从后半句推出。 3. 比较have t
11、o和must A. must的基本用法: 表示必须，强调说话人的主观意志、义务或命令。例：I must go now, or Ill be late. You must be here by ten oclock. 【注意】：表示“必须“时，must的否定式为neednt ，或dont have to ,而不是mustnt。Must I/we do it now？Yes, you must . No, you neednt / dont have to . 表示推测，“必定是，一定是”，一般只用于肯定陈述句，表示非常肯定。例：She didnt look at me. She must be
12、angry. 她不朝我看，一定是生气了。He is good at English. He must know the word. 他英语好，准知道这个词。You must be Mr. Jones.您肯定就是琼斯先生吧。 must对现在的状态或现在正发生的事情的推测时，must后面通常接系动词be 的原形或行为动词的进行式。 You have worked hard all day. You must be tired.你辛苦干一整天，一定累了。（ He must be working in his office. 他一定在办公室工作呢。 比较： He must be staying the
13、re. 他现在肯定呆在那里。 He must stay there. 他必须呆在那。 must 表示对已发生的事情的推测时，must 要接完成式。 I didnt hear the phone. I must have been asleep.我刚才没有听到电话，我想必是睡着了。 must表示对过去某时正发生的事情的推测，must 后面要接不定式的完成进行式。 -Why didnt you answer my phone call? -Well, I must have been sleeping, so I didnt hear it. 否定推测用cant，“不大可能” If Tom did
14、nt leave here until five oclock, he cant be home yet.B. 与have to对比使用 1) 两词都是必须的意思，have to 表示客观（现实条件逼迫等）的必须， must 表示说话人主观上的看法，既主观上的必要或义务。 My brother was very ill, so I had to call the doctor in the middle of the night.我弟弟病得很厉害，我只得半夜里把医生请来。(客观上需要做这件事) He said that they must work hard. 他说他们必须努力工作。（主观上要
15、做这件事） 2) have to有人称、数、时态的变化，要视主语的不同而变化；而must只有一种形式。 He had to look after his sister yesterday. 例：I / You / We / They have to. He / She / It has to. You dont have to.Does she have to?have to =have got to，意思是“必须，不得不”。 3）在否定结构中： dont have to表示“不必，没有必要”， mustnt 不表示推测，而表示禁止 You dont have to tell him abou
16、t it.你不一定要把此事告诉他。 You mustnt tell him about it.你一定不要把这件事告诉他。 情态动词表示推测的时态用法 ： must, can, could, may, might 皆可表示推测，语气强度逐次降低，其用法如下： 1）情态动词+动词原形；表示对现在或将来的情况的推测，此时动词通常为系动词。 I dont know where she is, she may be in Wuhan. 2）情态动词+动词现在进行时；表示对现在或将来正在进行的情况进行推测。 At this moment, our teacher must be correcting ou
17、r exam papers. 这时，我们老师想必在批改试卷。 3）情态动词+动词完成时；表示对过去情况的推测。 We would have finished this work by the end of next December. The road is wet. It must have rained last night. 地是湿的，昨天晚上一定下雨了。 4）情态动词+动词的现在完成进行时；表示对过去正在发生事情的推测。 Your mother must have been looking for you. 你妈妈一定一直在找你。 5）推测的否定形式用cant / couldnt（不可
18、能），may not/might not（可能不） 不能使用mustnt 不表示推测，而表示禁止，意义为“禁止，不准”。 Mike cant have found his car, for he came to work by bus this morning. 迈克一定还没有找回他的车，因为早上他是坐公共汽车来上班的。 疑问句中表推测“可能”：用can, could, might,而不能用may. Could he have finished the task?他可能把任务完成了吗？Can he be at home now? 他现在能在家吗？情态动词+have+过去分词 和虚拟语气的区分（
19、高中）： 1) may(might) have + done sth, can (could) have + done sth表示过去，推测过去时间里可能发生的事情。 Philip may (might) have been hurt seriously in the car accident. Philip can (could) have been hurt seriously in the car accident. 2 )must have +done sth，对过去时间里可能发生的事情的推测，语气较强，具有肯定，谅必的意思。 -Linda has gone to work, but
20、her bicycle is still here. -She must have gone by bus. 表示与现在事实情况相反的虚拟语气的表达方式： 3) ought to have done sth, should have done sth 本应该做某事，而事实上并没有做。否定句表示不该做某事而做了。 You ought to (should) have been more careful in this experiment. He ought not to have thrown the old clothes away.（事实上已扔了。） ought to 在语气上比shoul
21、d 要强。 4) neednt have done sth本没必要做某事 I dressed very warmly for the trip, but I neednt have done so. The weather was hot. 5) would like to have done sth本打算做某事 I would like to have read the article, but I was very busy then. 4. should和ought to should 和ought to 都为应该的意思，可用于各种人称。但是should谈的是自己的主观看法，ought
22、to则更多反映客观情况，在谈到法律、义务和规定时使用。 -Ought he to go? -Yes. I think he ought to. She is your mother, so you ought to support（赡养） her We ought to go and see Mary tomorrow, but I dont think we will should的用法 ：（1）表示说话人的猜测，估计应该 That should be Janet coming upstairs now. 正在上楼的准是珍妮特。 (2) 表示劝告或建议。例如： He should learn
23、 how to drive the car. ought to的用法：(1) 用于第一人称，表示有责任或有必要去做某事，与should相比，语气较弱。例如：We ought to be more careful with our homework.我们应当更加认真地做作业。I really ought to phone my mother.我确实应该给妈妈打个电话。(2) 用于第二、三人称，表示建议或劝告。例如：You ought to follow Mr. Wangs advice.你应当听王老师的话。You ought not (oughtnt) to go.你不应当去。(3) 表示对现在
24、或将来某种可能性的推测，这种推测是可信的。例如：Henry ought to be here soon. He left home at six.亨利应当很快就到,他六点就从家里出来了。Tom ought to be home now.汤姆现在该到家了。5. need和dare的用法A. need的基本用法：need的基本词义是“需要”，它既可作情态动词，又可作实义动词。 need用作情态动词时，只用于否定句和疑问句。它只有一种形式，后接动词原形。例：I dont believe you need worry. 我相信你没有必要焦急。Need we go so soon?我们需要这么早就去吗？
25、 Yes, we must. / No, we neednt.是的，必须。不，不必。So I neednt tell him, need I? 所以我不需要告诉他，对吧？【注意】：Need I/we？Yes，you must ./No, you neednt / dont have to .请比较以下两句话的不同意思：You neednt buy the coat. 你没有必要买那件外衣。（你还没买）You neednt have bought the coat. 你没有必要买这件外衣的。（而你却买了） need用作实义动词时，有时态、人称和数的变化。如果人作主语，一般后接带to的动词不定式。
26、即need to do sth；如果物作主语，一般后用need to be done 或need doing sth。例如：I need to look up this word in the dictionary. My watch needs mending/to be mended. 我的手表需要修理了。We dont need to work today. (= We neednt work today.) Does he need to go right now? (= Need he go right now?) need 的被动含义：need, want, require, wo
27、rth（形容词）后面接doing也可以表示被动： need doing =need to be done B. dare的用法用于表示“敢于”之意。做情态动词，没有人称和数的变化，主要用于否定句、疑问句和条件状语从句中 Dare you tell her the truth? Yes, I dare. /No, I darent. How dare you accuse me of lying! He darent admit this.用作实义动词时，其变化与一般的实义动词相同。在肯定句中，dare后接动词原形；否定句中，dare后既可接带to的不定式，也可接不带to的不定式。Only a
28、few journalists dared to cover the story.He doesnt dare (to) go there alone.Dont you dare (to) touch it?6. had better 和would ratherA. had better的基本用法：had better常略作d better。现代语法认为它是一个助动词，因为它后接动词原形。had better do sth意思是“最好做某事；还是做某事比较好”。 否定形式：had better not do sth意思是“最好不做某事；还是不做某事比较好” had better 相当于一个助动
29、词，它只有一种形式，它后面要跟动词原形。 Had better do sth had better not do sth 例：Youd better get some sleep. 你最好睡一会儿。Youd better not do that again. 你最好别再做那件事。What had we better do now? 我们现在怎么做才好呢？Hadnt we better tell her the truth? 我们是否最好不告诉她真相?【注意】：Youd better.表示劝告或委婉的命令，对长辈不宜使用。 had better have done sth表示与事实相反的结果，意
30、为本来最好。 You had better have come earlier. B. Would rather表示宁愿 would rather do would rather not do would rather than宁愿而不愿。还有would sooner, had rather, had sooner都表示宁愿、宁可的意思。 If I have a choice, I had sooner not continue my studies at this school. I would rather stay here than go home. = I would stay here rather than go home. 典型例题 -Shall we go skating or stay at home? -Which _ do? A. do you rather B. would you rather C. will you rather D. should you rather 答案
