情态动词知识点(共6页)

1、一 表能力Can /be able to 表现在的能力； will be able to 表将来的能力；could/was/were able to 表过去的能力如：I am starving to death. I can eat two bowls of rice now.现在的能力If you have a good sleep, you will be able to work out this problem.将来的能力The fire spread through the hotel very quickly but everyone was able to get out.（过去

2、有能力做并且成功地做了某事）I could have worked out the problem, but I didnt .（过去有能力做但未做）单项选择I should have been there,but I _not find the time.A. would B. could C. might D. shouldIn spite of many difficulties, he _save the boy from the ruins.A. had to B. would C. could D. was able to 二表推测（可能性）1.可能性可分为客观的可能性和具体事情实

3、际发生的可能性两种。所谓客观的（理论的）可能性即不涉及具体某事是否发生，此种用法常常可以说明人或事物的特征。情态动词can 可用于肯定句中表示客观的（理论的）可能性，而表示具体事情实际发生的可能性时，can 一般不用于肯定句。如：Accident can happen on such rainy days.客观的可能性Peter may come with us tonight, but he isnt sure yet.(实际可能性，不用can ) 2.表具体事情实际发生的可能性：（1）表示具体事情实际发生的可能性的层次比较（见下表）：词形肯定式否定式疑问式Must必定，必然/Will很可能

4、，大概不会，不该会-吗？Would 可能性比will 小语气比wont弱语气比will吗Should说话者有较大的试探性/Ought to 说话者有较大的试探性（含义同should）/Can /不可能有可能吗？Could 可疑的可能不可能语气比can 弱May或许，也许，也未可知，也说不定可能不/Might比may 还弱比may not 还弱/ （2）表示具体事情实际发生的可能性时，may,must 常用于肯定句，一般不用于否定句和疑问句（may not 表示“可能不”）：can 常用于否定句、疑问句或感叹句中，表示疑惑、惊讶或不相信的意思；could既可用于肯定句又可用于否定句、疑问句中。如

5、：This cant/couldnt be done by him.(表示不相信)This may not be done by him.(表示不确定)He could be on his way home now.(could 不如may/might常用)Can this be done by him？（表示疑惑、惊讶）Mr. Bush is on time for everything. How can it be that he was late for the opening ceremony?(表示疑惑、惊讶)I didnt hear the phone. I must have b

6、een asleep.(表肯定)-Are you coming to Jeffs party?-Im not sure. I might go to the concert instead.(表不确定)题组训练用 can,could, may, might, must填空Sorry,Im late. I _have turned off the alarm clock and gone back to sleep again.That _not be Mary. Shes in hospital.How _you be so stupid?3.would, could, should, mig

7、ht 并不一定与过去时间有关，而是表示可能性弱于它们相应的现在时形式。如：This may/might be done by him.(后者比前者语气弱)4.should/ought to 表推测时，表示说话者有较大的试探性。 如：He ought to /should be here in time-he started early enough.We should arrive before dark.The roads should be less crowed today.三表请求、允许、允诺1.当对方是决策者时，你代表你（们）自己（I ,we）或代表第三者（he ,she, they

8、）向对方(you)请示或提出建议时用：Shall I (we)-?Shall he/she/they-?Would/will you -? 如：Shall we begin our class ?Shall the driver wait outside?When shall my father be able to leave hospital?Would you do me a favor?2.could/might/would/should 表委婉语气的功能。 如：-could/might I use your bike tomorrow morning ? -Yes,you can/m

9、ay.(否定：No, Im afraid not)不可说：Yes, you could/might. 回答允许时，用could/might表委婉是不恰当的。如：-could I borrow your dictionary?-Yes,of course you can.题组训练单项填空：The room is dirty._we clean it? -of course.A. Will B. Shall C. would D. Do -_he come to see you ? -of course, please. And Id rather he told me the truth.A.

10、Will B。Shall C. Would D. Do 3.当你自己（I）是决策者，给对方（you）或第三者（he,she,they）以命令、警告、允诺或威胁时，要用shall 。此外， 当宣布法律、规定时， 也要用shall 。如：You shall leave the room at once, and he also shall.=(I order you and him to leave the room at once.)It has been announced that candidates shall remain in their seats until all the pa

11、pers have been collected.题组训练单项填空：He asked me for this book many times. Please tell him he _have it tomorrow.A.must B. may C. shall D. both B and CIt has been announced that all the students _put on masks()before going to school in case they are infected with SARS virus.A. shall B. will C. need D. m

12、ay四表必要性1.must 常用来表示必要性，意为“必须”。 表示现在或将来必须做某事用“must+动词原形”；表示现在或将来不必做某事时，用 dont have todo sth或dont need to do sth 或neednt do sth；表示过去没必要做某事时 ，分为以下情况：当表示过去没必要做某事，但事实上却做了，用neednt have done sth ；当表示过去没必要做某事，而不涉及是否已经做了，可用didnt have to do sth或didnt need to do sth 或It was not necessary to do sth等。如。You needn

13、t have worked that late last night . It was harmful to your health.-Did you work very late last night?-No,I didnt. I didnt need to work very late.2.should也可以表示必要性，意为“（义务上）应该”。Should表必要性时，在语气上比must (必须)弱。“should+动词原形”表示现在或将来应该做某事（的必要性）；“should+have +过去分词”表示过去本应该做某事（的必要性）如：I should go and visit him th

14、is afternoon, but I wonder if I will be free.（表示将来的必要性）You should have come to the conference yesterday. What was the reason for your absence?（表示过去的必要性） 题组训练完成下列句子You _(没必要告诉)her the news for I had told her about it earlier.I _(没必要非得出去)but I wanted a breath of fresh air.We _(本该买)a new lock for the f

15、ront door.五 表示“宁愿做某事”时，可使用下面这些句式 Would rather do sthWould rather do sth than do sth Would do sth rather than do sthWould rather sb did sthPrefer to do sth Prefer to do sth rather than do sth Prefer doing sth to doing sth 六情态动词+have done用法一览表情态动词+完成时意义例句Must have done“想必/准是/一定做了某事”，否定式为cant/couldnt h

16、ave done It must have rained last night,for the road was quite muddy.The lights were out. They must have been asleep.Can/could have done本来能够 过去可能会You could have come 5 minutes earlier.Can he have gone to his aunts?Can/could not have done过去不可能 过去没能I saw Mr.Wang just now.he couldnt have gone to Beijin

17、g.May/might have done“也许/或许已经-”一般只用于肯定句和否定句中（在否定句中表示“可能不”），不用于疑问句。用might则表示语气更加不肯定。Its too late. I think he may have gone to bed.He may not have finished the work.She might have caught a cold.Should/ought to have done“本该做某事，而实际上未做”You should have come to the meeting earlier.You ought to have done th

18、is exercise more carefully.Shouldnt/ought not to have done“本不该做而做了某事”You shouldnt have told her the truth.Neednt have done表示“做了本来不必去做的事”注意：didnt need to do 表示“没必要做而实际上也没有做某事”。You neednt have taken a taxi here,for it was very near to my house.I didnt need to clean the windows. My brother did it.Had b

19、etter have done用于事后的建议，含轻微责备的口吻，意为“要是当时做了某事就好了”，其否定式had better not have done 表达相反的含义。You had better have started earlier.You had better not have scolded her.Would rather have done 表示 “宁愿当时做某事”，其否定式 would rather not have done 表达相反的含义，两者都表示“后悔”之意。I would rather have taken his advice.I raised objection

20、s at the meeting,but now I would rather not have done that.Would like/love to have done表示过去愿意做某事，但未做成。I would love to have gone to the party last night but I had to work extra hours to finish a report. 题组训练单项填空：I stayed at a hotel while in New York. -Oh,did you ? You _with Barbara.A. could have stay

21、ed B. could stay C. would stay D. must have stayed.I was really anxious about you. You should _home without a word.A. mustnt leave B. shouldnt have left C. couldnt have left D. neednt leaveHe hesitated for moment before kicking the ball, otherwise he _a goal.A. had scored B. scored C. would score D。

22、 would have scored七情态动词其他用法要点1.cannot but do sth 不得不，只好 如：I cannot but choose to go.2. may well 和 may as well 结构（） “may well+ 动词原形 是一种常用结构，意为“完全能，很可能”，相当于 to be very likely to .如：He may well be proud of his son.Her appearance has changed so much that you may well not recognize. （2） “may/might as wel

23、l+动词原形”意为“最好，满可以，倒不如”，相当于had better或to have no strong reason not to. 如 ： You may as well do it at once.We may as well stay where we are.3.Can not （或never）等否定词与enough 连用表示“再也不为过”。 4.may可以用于祈使句，表示祝愿。如：May we never forget each other.May you return in safely.5.why/how+should 结构表示说话人对某事不能理解、感到意外、惊异等意思，译为

24、“竟会”如：Why should you be so late today?How should I know?【题组训练】翻译下列句子：我不得不佩服你的勇气。（cannot but）她很可能拒绝和你谈话。（may well）你最好留在这里过夜。（may as well）祝您的生活美满、幸福。（may）祝您成功！（may）我真的不明白你凭什么认为这件事是我干的。（should）6.must 表示“偏要、硬要”做某事。如：-how old are you, madam?-If you must know, Im twice my sons age.7.may 作“可以”讲时，其否定式常用“mustnt”表示“被禁止”；must作“必须”讲时，其否定式是“neednt”,表示“不必”如：May I use you car?No,you mustnt.(