1、情态动词的用法A. can; could; be able toCan 1. 表示“ 能力”( 此时过去时是 could) 2.表示许可、请求， “可以” 。-Can/Could I go now?3 表示推测, 把握很大,could 也可表推测, 把握比 can 小。-Look! Someone is coming! Who can it be?-It cant be him. He has gone to Paris.（不可能）/ He could be here soon. 他很快就来。4 表示感情（惊异/ 不耐烦） “究竟，到底” （主要用于否定句，疑问句和感叹句中。 ）How can
2、 you be so foolish?What can it possibly be? 到底那是怎么一回事?They cant be working at this time of day. 5 肯定句中客观存在的可能性。 “有时会，偶尔”It can be quite windy there, especially in spring. Could 1.表示能力， can 的过去式，过去能够Could you speak English then? 那时候你会说英语吗? 2. 请求允许（委婉语气） （问句的答语不用 could，而用 can， ）Could Can I use your pe
3、n? ” “Yes, of course you can.”/ No, Im afraid not. 3. 表示推测可能性（肯，否，疑）We could go there this summer. 今年夏天我们可能要去那儿。( 将来可能性)You could be right, but I dont think you are. 你可能是对的，但我并不认为你是对的。4. could have done 对过去推测，可能已经。 。 。本来能够却没做，差点就He cant couldnt have seen her there. 他不可能在那儿见到她。 He could have gone hom
4、e. 他可能已回家了He could have told her, but he didnt choose to. 他本来可以告诉她的，但他却没有。B. may 和 might1.表示允许许可，might 提问更委婉。-May/Might I watch TV after supper?-Yes, you may./ Yes, please./ Certainly.-No, you mustnt. / No, you may not. / No, you cant./No, youd better not.2. 表示推测，有“ 或许”、 “可能”的意思。might 把握更小。疑问句用 can/
5、 could. He may/might be right./ I hear there may be a few copies left. He may/might come today (tomorrow).3. may 表示祝愿，倒装。 May +主语+ 动词原形。May you succeed!/May you all be happy. may might as well意为“ 不妨”、“ 还是为好”等，用 might 比用 may 语气更委婉。如： Im ready，so I might as well go now我已准备好，因此不妨现在就走。Theres nothing to
6、do, so I may might as well go to bed. may well. 完全可能C. must, have to Must 1. 表示“必须”。否定式 mustnt 表示“不可以” 、 “不准”、 “禁止”等。Everybody must obey the rules/You mustnt lend it to others./You mustnt speak like that to your mother.在回答有“must” 的询问时， - Must I go now? - Yes, you must. -No, you neednt. / No, you don
7、t have to.2. must 表示推测（“一定” 、 “必定”） ，表肯定的推测, 其否定的推测用 cant，表示“不可能”。You must be hungry after the long walk. / It cant be Jim, for he has gone to Beijing. The Chinese language must have the large number of speakers.3must 表示说话人不耐烦的态度， “干嘛偏要”must + have + done，表示对过去事物的肯定推测。 “一定做过.” He must have told my p
8、arents about it. 他一定把这件事情告诉我父母亲了。must 表示推测时，其反意疑问句应根据动词的实际时态而变化。如： It must be nice to take a walk here, isnt it? Tom buys a lot of apples ,he must like eating them, doesnt he？ Must have done 的反意疑问句有三种情况:从句中含有过去的时间状语,反意疑问句用过去时. The ground is wet , it must have rained last night, didnt it?从句中含有过去完成时的时
9、间状语,反意疑问句用过去完成时. By the end of last term, we must have learnt 2000 words, hadnt we?若从句中不含任何时间状语,反意疑问句用现在完成时 We must have been met somewhere (before), havent we?must 表示“必须” “有必要”时，反义疑问句部分用 mustnt.? 或 neednt .? You must go home right now, neednt you?must 用否定形式 mustnt 时，附加疑问句部分用 may 或 must?You mustnt c
10、heat in the examination, must you?3. 表示与说话人愿望相反及不耐烦意为“偏要” -_you make so much noise? -Sorry, I will take care not to. A Must B Can C May D Would4. must 和 have to 的区别:D. ought to/ should/ shallOught to ought to 用于反映客观情况或涉及义务和规定时，常译作“应该”、 “应当”(和should 差不多， 只是语气较强 )，有时表示非常可能的事情。 There ought not to be mu
11、ch noise in a hospital. - Ought he to go? - Yes, he ought to. If she is completely well, she ought to be back at school today.ought to have done 指过去动作 ,表示一件事情该做而未做。 ought not to have done 表示一件不该做的事情却做了。should 1.用于表示劝告和建议， “应该” 表示自己的主观看法 ,语气比 ought to 弱。should + have done 指过去动作,表示一件事情该做而未做。 should no
12、t + have done 表示一件不该做的事情却做了。 - Who did it sound like? Anybody you know?- Well, perhaps Jeff. I should have asked who was calling before he hung it up.2.表推测， “按道理，按常理应该”They should have arrived by two o clock.3.表示惊讶,赞叹，不满，责备 “竟然”I am sorry that you should do such a thing.4. 用于 if 引导的虚拟条件句中，表示一件事听起来可能
13、性小，但也不是完全不可能。有“万一” 的意思Should I be free tomorrow, Ill come.Ask Tom to ring me up if you should see him.shall1. shall 作为情态动词，用于第二、第三人称， 陈述句，表示说话人的意愿，有 “命令”、 “警告”、 “威胁”、 “强制”、 “允诺” 等意思。 “必须，应，可以” You shall do as I say. （命令） Tell him that he shall have the book tomorrow. （允诺） You shall be punished if yo
14、u break the law. (表警告)2. 用于第一、第三人称, 在疑问句中，shall 用来征询对方意见。 “好吗？” “要不要？”Where shall I wait for you?/ Shall he come at once?/ Shall we start the meeting now?3.在条约规定法令等文件中表示义务或规定，用于第三人称The new regulation shall take effect on June 1st.E. will 和 would 1) 表示“意志”、 ”决心” 、 “意愿”，可用于多种人称。will 指现在，would 指过去。 I w
15、ill tell you all about it./ He wont go.(2) 表示询问对方的意愿或向对方提出请求 ,在疑问句中用语第二人称时，委婉语气 would. Im going to go shopping after school. Will you go with me? Will/would you please give him a message when you see him?(3) 表示习惯动作，有“总是”、 “惯于”的意思。过去式 wouldHell talk for hours if you give him the chance.(4) 表示功能， “能”T
16、he door wont open. / The car wont start.(5)will 用于叙述真理,客观规律时“会”Oil will float on water. / Fish will die without water.F. need 和 dare1. need 表示 “需要”、 “必须”。通常用在否定句或疑问句中。 He neednt pay for it.- Need you go now? - Yes, I must. - No, I neednt.2. dare 表示“敢 ”。通常用于否定句、疑问句、条件从句和 if/whether 引出的宾语从句中。 How dare
17、 you say Im unfair? She dare not do so. He asked me if I dared speak English in public.need 和 dare 也可用作行为动词，变化与一般动词相同 She didnt need to go. - Who dares to go? - - I dont dare (to) go.I dare say 作插入语,我想, 大概, 可能, 或许“neednt + have done” 表示过去做了没必要做的事情。 You neednt have taken it seriously. 这件事情你不必太认真。G. h
18、ad better “最好” We had better go now. Yes, we had (wed better / we had better). Hadnt we better stop now? (Had we better not stop now?) I think Id better be going. （用于进行时态，表 “最好立即”） You had better have done that. （用于完成时态，表未完成动作） 情态动词+ have done1、must have done,“一定做过/ 一定已经 ”，表示对过去情况极大把握地推测，仅用于肯定句2、may
19、/might have done 也许做过某事（推测） ；本来可以做某事却没做3、cant have done 为否定句或疑问句 ,对过去的推测“不可能，一定没做过某事”could have done 本来可以做某事却没做4. neednt have done 表示”不必要做某事，但做了 ，而 neednt do 则表示” 不必做(也没做)”5.、ought to /should have done 表示” 本来应当做的却没做”oughtnt / shouldnt have done 本来不应该做某事却做了6、would/could/might/should + have done 用来表示与过去事实相反的虚拟语气7、would rather have done 表示”当时宁愿做了某事” ，否定形式：would rather not have donee.g. If I had been free that day, I would have gone with you.9、would like/love to have done 表示” 本想做某事” 而实际上未做。
