情态动词（Modal Verbs)can, could, may, might, will, would, shall, should, must和ought称为情态动词。它们 和 主要谓语动词一起构成谓语。绝大多数情态 动词的意思可以划分为两类。 一类是表示可能性：情态动词可以用来表示 某种情况是肯定的、或很可能的、或可能 的、或不可能的。另一类意思涉及必须做某事或允许做某 事之类的意思：情态动词可以用来表示 某人必须做某事、某人能做某事，如果 某事发生（或不发生）就会好一些，或 者某事是许可或禁止的。一、表示有把握的程度 情态动词可以表达对于某一事实 或事件有把握的各种不同程度。a完全有把握(肯定的或否定的） shall用于第一人称： I/We shall be away tomorrow. I shant be late on Wednesday. 2. will 用于各种人称： Thats the phone. Thatll be Tony. Things will be right. It wont rain this evening. Youll be right. 3. must只用于肯定句中： He decided Franklin must be suffering from a bad cold. 4. cant和couldnt表示现在或将来不可能， couldnt用于间接引语中，表示过去不可能： That cant be Mr. Smithhes in New York. I knew it couldnt be Mr. Smith. He couldnt be at home. 5. would, wouldnt 用于间接引语中，表示过 去可能或不可能： I told you wouldnt be ready in time.1. should, shouldnt, ought to, oughtnt to, may well (很有可能）, may, may not （可 能、可能不） : She should/ought to be here soon. It shouldnt/oughtnt to be difficult for you to work out the problem. 3. We may be buying a new flat. 4. The list may not be complete. 5. “I think its going to rain.” “You may well be rightthe sky is really black.b很有可能/可能C可能性小might, mightnt, could,它们不是may, can的 过 去式，它们都可以用来谈论现在和将来, could比may 和might更不可能： I might see you againwho knows? Things might not be as bad as they seem. We could all be millionaires one day.d在理论上可能或现实可能性 can可以用于肯定句中表示理论上的可能 性，或与be动词连用，表示有时： 1. Poor posture (姿势）can cause neck ache, headaches and breathing problems. 2. New England can be very warm in September. 3. Can gases freeze?2.表示某事将会实际发生，或真实情况的现实可能 性通常用may, might或could: 1)-I think Labour are going to win.-You may be right. 2)-Where is Emma?-I dont know. She may be out shopping. 3) Peter might call. If he does, ask him to ring later. 4) She didnt say hello. She may not have recognized you. 5) -Wheres Sarah?-She may/ might/ could be at Joes place.e在条件句中表示有把握或可能 would, wouldnt, could, couldnt, might, mightnt可以用在含有条件句的主句中表示可能： If we had enough time, things would be easy. I wouldnt do this if I didnt have to. If John came we could all go home. I couldnt do anything without your help. It mightnt be a bad thing if we took a short holiday.询问可能性 might表示可能性,可以和could/can一样用在问 句中，询问可能性。也可用于肯定、否定句中 。 Might it be possible to make computers the size of a pinhead one day? Might/ Could/ Can he still be working? Might/ Could/ Can he have been waiting long? 4. Might/ Could he have left by tomorrow?“could, might, ought to, should, would和neednt +have +过分的用法1.could, might, ought to, should, would和 neednt + have +过分,常用来表示非真实的情 况: Did you see him fall? He could have killedhimself. 2. You should have called-I was gettingworried. 3. I would have gone abroad if I had had more money. 4. She neednt have sent her mum flowers.情态动词 modal verbs的 特点1）有特定的词义 2）没有人称和数的变化 3）其后加动词原形(do), have done ,be doing.情态动词 情态动词 1。区别must / have to Must表示人在主观上认为的必要、必须、一定要 Have to表示受环境或习惯支配的客观必要 “不得不”，能用于更多时态。1)Soldiers _obey officers.2)Its raining outside.We_stay at home. 3As he had broken his leg， he _lie in bed.易混易错用的情态动词 musthave to had to2。表示能力: can, could, be able to*be able to 能用于各种时态。can / could 只能表示现在或过去的能力。*was / were able to : “设法做成某事”相当于 managed to do sth. succeeded in doing sth.。Eg.Though they were trapped in the big fire,they _escape.were able to4。注意对need问句的回答:-Need I finish the work today?-Yes, _.No, _.No, _.you mustyou needntyou dont have to-Shall I tell John about it?-No, you _.-Must we do it now? -No, you _.neednt (dont have to)neednt (dont have to)6.表示推测情态动词的重要用法.肯定的推测可能的推测否定的推测疑问的推测must对将来 对现在 对过去情态动词may, mightcant, couldntcan, could+ V. + V. + have done 常见must be + be doing+ V. + V. + have done+ be doing可以用not表示“可能不” +V. + V. + have done+ be doing+ V. + V. + have done+ be doing2. can (用于疑问句中）， cant, could, may, might, should, ought to, will, must + have + 过分可以表示对过去发生的事情作出推断： Where can he have gone? We cant have taken it upstairs this morning! I may / might/ could have come to a wrongconclusion. 4. That was a bad place to go skiing. You might have broken your leg.5. -A woman phoned while you were out.-It must have been Kate. John should/ ought to have arrived yesterday. 7. I wonder why we havent heard from him- do you think he wont have got our letter yet? 8. We cant go and see them now- theyll have gone to bed.3.can (用于疑问句中）， cant/ could/ may/ might/ should/ ought to/ will/ must + have + 过分也可以表示某事可能已经发生，该用法 类似现在完成时和将来完成时： 1. Ill try phoning him, but he might have gone out by now. 2. By the end of this year I might have saved some money. 3. John should /ought to have left by tomorrow. 4. Thatll have been Roland. He said hed be back