1、情态动词用法归纳情态动词用法归纳 情态动词有can (could), may (might), must, have to, shall (should, will (would), dare (dared), need (needed), ought to等。 情态动词无人称和数的变化；不能单独使用，必须与其后的动词原形构成谓语 一、 can, could 1) 表示能力（体力、知识、技能）。 Can you lift this heavy box?（体力） Mary can speak three languages.（知识） Can you skate?（技能） 此时可用be able
2、to代替。Can只有一般现在时和一般过去式；而be able to则有更多的时态。 Ill not be able to come this afternoon. 当表示“经过努力才得以做成功某事”时应用be able to，不能用Can。如： He was able to go to the party yesterday evening in spite of the heavy rain. 2) 表示请求和允许。 -Can I go now? - Yes, you can. / No, you cant. 此时可与may互换。在疑问句中还可用could, might代替，不是过去式，只是
3、语气更委婉，不能用于肯定句和答语中。 - Could I come to see you tomorrow? - Yes, you can. ( No, Im afraid not. ) 3) 表示客观可能性（客观原因形成的能力）。 Theyve changed the timetable, so we can go by bus instead. This hall can hold 500 people at least. 4) 表示推测（惊讶、怀疑、不相信的态度），用于疑问句、否定句和感叹句中。 Can this be true? This cant be done by him. Ho
4、w can this be true? 二、 may, might 1) 表示请求和允许。might比 may语气更委婉，而不是过去式。否定回答时可用cant 或mustnt，表示“不可以，禁止”。 -Might/ May I smoke in this room? - No, you mustnt. - May/Might I take this book out of the room? - Yes, you can. (No, you cant / mustnt. ) 用May I.？征徇对方许可时比较正式和客气，而用Can I.？在口语中更常见。 2）用于祈使句，表示祝愿。 May y
5、ou succeed! 3) 表示推测、可能性（不用于疑问句）。 might不是过去式，它所表示的可能性比may小。 1He may /might be very busy now. 2Your mother may /might not know the truth. 三、 must, have to 1) 表示必须、必要。 You must come in time. 在回答引出的问句时，如果是否定的，不能用mustnt（禁止，不准），而用neednt, dont have to（不必）. - Must we hand in our exercise books today? - Yes,
6、 you must. - No, you dont have to / you neednt. 2) must是说话人的主观看法， 而have to则强调客观需要。Must只有一般现在时， have to 有更多的时态形式。 1 he play isnt interesting, I really must go now. 2 I had to work when I was your age. 3) 表示推测、可能性（只用于肯定的陈述句） 1 Youre Toms good friend, so you must know what he likes best. 2 Your mother
7、must be waiting for you now. 四、 dare, need 1) dare作情态动词用时, 常用于疑问句、否定句和条件从句中, 过去式形式为dared。 1 How dare you say Im unfair? 2 He darent speak English before such a crowd, dare he? 3 If we dared not go there that day， we couldnt get the beautiful flowers. 2) need 作情态动词用时, 常用于疑问句、否定句。在肯定句中一般用must, have to
8、, ought to, should代替。 1You neednt come so early. 2. - Need I finish the work today? - Yes, you must. / No, you neednt. 3) dare和 need作实义动词用时， 有人称、时态和数的变化。在肯定句中，dare后面常接带to的不定式。在疑问句和否定句中，dare后面可接带to或不带to的不定式。而need后面只能接带to的不定式。 1. I dare to swim across this river. 2. He doesnt dare (to) answer. 3. He n
9、eeds to finish his homework today. 五、 shall, should 1) shall 用于第一人称，征求对方的意见。 What shall we do this evening? 2) shall 用于第二、三人称，表示说话人给对方的命令、警告、允诺或威胁。 1. You shall fail if you dont work hard.(警告) 2. He shall have the book when I finish it.(允诺) 3. He shall be punished.(威胁) 六、 will, would 1) 表示请求、建议等，wou
10、ld更委婉。 Will / Would you pass me the ball, please? 2) 表示意志、愿望和决心。 1. I will never do that again. 2. They asked him if he would go abroad. 3) would表示过去反复发生的动作或某种倾向。would表示过去习惯时比used to正式，且没有“现已无此习惯”的含义。 1. During the vacation, he would visit me every other day. 2. The wound would not heal. 4) 表示估计和猜想。
11、 It would be about ten oclock when she left home. 七、 should, ought to 1) should, ought to表示“应该”，ought to表示义务或责任，比should语气重。 1. I should help her because she is in trouble. 2. You ought to take care of the baby. 2) 表示劝告、建议和命令。should, ought to可通用，但在疑问句中常用should。 1. You should / ought to go to class ri
12、ght away. 2. Should I open the window? 3) 表示推测 should , ought to (客观推测), must(主观推测)。 1.He must be home by now. (断定他已到家) 2.He ought to/should be home by now.(不太肯定) 3. This is where the oil must be.(直爽) 4. This is where the oil ought to/should be.(含蓄)1 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，只表示期待或估计某事的发生。
13、2） 情态动词 除ought 和have 外，后面只能接不带to 的不定式。 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。 2 比较can 和be able to 1）can could 表示能力；可能 (过去时用could), 只用于现在式和过去式(could)。be able to可以用于各种时态。 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
14、时。 d. 用于句首表示条件。 e. 表示成功地做了某事时，只能用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. 注意：could不表示时态 1）提出委婉的请求，（注意在回答中不可用could）。 - Could I have the television on? - Yes, you can. / No, you cant. 2）在否定，疑问句中表示推测或怀疑。 He co
15、uldnt be a bad man. 他不大可能是坏人。 3 比较may和might 1） 表示允许或请求；表示没有把握的推测；may 放在句首，表示祝愿。 May God bless you! He might be at home. 注意： might 表示推测时，不表示时态。只是可能性比may 小。 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.
16、 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。 4 比较have to和must 1) 两词都是必须的意思，have to 表示客观的需要， must 表示说话人主观上的看法，既主观上的必要。 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。（主观上要做这件
17、事） 2) have to有人称、数、时态的变化，而must只有一种形式。但must 可用于间接引语中表示过去的必要或义务。 He had to look after his sister yesterday. 3） 在否定结构中： dont have to 表示不必 mustnt 表示禁止， You dont have to tell him about 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。 5 must表示推测 1) must用在肯定句中表示较有把握的推测，意为一定。 2) must表对现在的状态或现在正发
18、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。（对现在情况的推测判断） He must be working in his office. 他一定在办公室工作呢。 比较： He must be staying there. 他现在肯定呆在那里。 He must stay there. 他必须呆在那。 3) 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 b
19、een asleep. 我刚才没有听到电话，我想必是睡着了。 4) 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. 5) 否定推测用cant。 If Tom didnt leave here until five oclock, he cant be home yet. 如果汤姆五点才离开这儿，他此时一定还未到家。 6 表示推测的用法 can, could, may, might,
20、 must 皆可表示推测，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 our 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 nex
21、t December. 明年十二月底前我们很可能已完成这项工作了。 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，疑问形式用cant, couldnt表示。 Mike cant have found his car, for he came to work by bus this morning. 迈克一定还没有
22、找回他的车，因为早上他是坐公共汽车来上班的。 注意：could, might表示推测时不表示时态，其推测的程度不如can, may。 7 情态动词+ have +过去分词 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) m
23、ust 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 her bicycle is still here. -She must have gone by bus. 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 hav
24、e thrown the old clothes away.（事实上已扔了。） ought to 在语气上比should 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. 8 should 和ought
25、to should 和ought to 都为应该的意思，可用于各种人称。 -Ought he to go? -Yes. I think he ought to. 表示要求，命令时，语气由 should（应该）、had better最好）、must（必须）渐强。 9 had better表示最好 had better 相当于一个助动词，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 It is pretty cold. Youd better put on my coat. Shed better not play with
26、the dog. had better have done sth表示与事实相反的结果，意为本来最好。 You had better have come earlier. 10 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 r
27、ather 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B。本题考查情态动词rather的用法，would rather +do sth 意为宁愿，本题为疑问句，would 提前，所以选B。 11 will和would 注意： 1）would
28、like； Would like to do = want to 想要，为固定搭配。 Would you like to go with me? 2）Will you? Would you like? 表示肯定含义的请求劝说时，疑问句中一般用some, 而不是any。 Would you like some cake? 3）否定结构中用will，一般不用would, wont you是一种委婉语气。 Wont you sit down? 12 情态动词的回答方式 问句 肯定回答 否定回答 Need you? Yes, I must. No,I neednt Must you? /dont ha
29、ve to. 典型例题 1）-Could I borrow your dictionary? -Yes, of course, you_. A. might B. will C. can D. should 答案C.could表示委婉的语气，并不为时态。答语中of course，表示肯定的语气，允许某人做某事时，用can和 may来表达，不能用could或might。复习： will 与you连用，用来提出要求或下命令。should与you 连用，用来提出劝告。 2）-Shall I tell John about it? -No, you _. Ive told him already. A
30、. neednt B. wouldnt C. mustnt D. shouldnt 答案A。neednt 不必，不用。 wouldnt 将不, 不会的。 mustnt 禁止、不能。 shouldnt 不应该。本题为不需要，不必的意思，应用neednt。 3）-Dont forget to come to my birthday party tomorrow. -_. A. I dont B. I wont C. I cant D. I havent 答案B. will既可当作情态动词，表请求、建议、也可作为实义动词表意愿、意志、决心，本题表示决心，选B。 13 带to 的情态动词 带to 的情态动词有四个：ought to, have to, used to, be to, 如加上have got to ,(=must), be able to，为六个。它们的疑问，否定形式应予以注意： Do they have to pay their bill before the end of the month? She didnt use to play tennis before she was fourteen. You ought not to have told her all about it. Ought he to see a hear
