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1、Grammar： Modal verbs 情态动词,情态动词（modal verbs)： 表示说话人的语气或情态，如请求、命令、愿望、能力以及可能性等。英语的情态动词有：,can/could may/might must shall/should will/would need have to,能够 可能 必须 应该 意愿 敢 需要 不得不,+ 动词原形,一、情态意义表示法,1.表示“能力”和“可能” a)表示“能力”，可用can, could, be able to can既能表示现在的能力，也表示将来的能力。 Eg.Look! I can do it. I cant do it now,
2、but I can do it later.,现在“能力”：can, be able to As I have got enough money, I can/am able to help her. Can: 某桩具体事情：eg.I can climb this cliff. 泛指一般的“能力”： He can drive a car. She cant play the piano.,将来“能力”： 通常 will/shall be able to Ill be able to speak German in another two months 具体某事：can Can you go a
3、nd see him tomorrow morning? If I can, I will do it.,过去“能力”: could, was/were able to 肯定句： Could：一般能力 She could play the piano when she was only six. was/were able to(及managed to)：具体事件 He was able to translate the article without a dictionary.,I talked a long time, and in the end managed to make her
4、believe me. 在否定句中，could既可以表示过去一般能力，也可表示过去某具体事情的能力. I couldnt/wasnt able to play the piano when I was at school.,b)表示“可能”，可用may, might, can, could may/might： 既可以表示现在的可能，也可表示将来的可能，might在口气上比may更委婉 现在：It may/might be true. 将来：He may/might leave tomorrow. 2.在疑问句中，用can，不用may。 Can they have missed the bus
5、? Yes, they may have.,may not重音落在助动词上，表示“不可能”，重音落在否定词上，表示“不许可” , 比较： He may not go tomorrow. He may not go tomorrow. 所以在书面语中，表示“不可能”常用cant,can/could表示现在的可能，口气上could比较委婉 Thats not mine. Whose can it be? It could be Johns. can常用于否定句和疑问句，而could不受此限。 If you dont have a guide, you could lose your way. It
6、 cant/couldnt be true. Can/could the news be true?,在肯定陈述句中，may与can的比较： Can指逻辑上的可能性，may指事实上的可能性 The road can be blocked.(按逻辑可能会堵，) The road may be blocked.(可能现在正堵着，事实上) Mr Reed is in poor health. He can be ill at any time. Mr Reed looks pale. He may be ill.,“may/might +have done/have been doing”,“can
7、/could +have done”表示过去的可能。 He may/might have missed the train. She may/might have been expressing her true feelings at that moment. She cant/couldnt have missed the train. “might/could +have done ”可以表示本来可能发生但没有发生的，或者本来可能完成却没有完成的动作， You might have finished the work last week. I could have passed the
8、examination, but I failed.,2表示“许可”和“不许” a)请求对方“许可”可用can, could, may, might. may/might较正式，could/might较委婉 表示给予“许可”通常用can/may,而不用could/might Could I use your phone? Yes, of course you can. Might I trouble you for a light? You may indeed.,b)表示“不许”可用may not或者cannot Can I go out for a moment? No, you cant
9、. May I use your car for a few days? No, you may not. may not也可表示根据一般规定的“不许可”，而不是说话人不许可 Borrowers may not take out of the library more than two books at a time. may not表示“不许可”的过去式不是might not He may not go.(=I dont permit him to go.) He might not go.(=Possibly he will not go.) 过去的不许可：He was not allow
10、ed to go.,3表示“义务”和“必然” a)表示“义务”，可用should, ought to, must. 表示要求，命令时，语气由ought to、 should、must渐强 Should/ought to表示“应该”，带有敦促，劝说之意，可交替使用，前者语气更强。 You should/ought to drink less. Should/ought to +have done:本应该 You should/ought to have asked my permission first. Must表示敦促或命令，必须。 I really must stop smoking.,表
11、示将来的“必须”，常用have to的一定形式（will/shall have to) 比较： We must do it again.(表示现在) Well have to do it again.(表示将来) 表示过去的“必须”，常用had to I had to leave at six yesterday. must有两种否定形式:第一个是must not,表示“不许”、“禁止”,相应的半助动词是be to的否定形式be not to You mustnt talk like that. You are not to talk like that.(不许你如此讲话。),第二个否定形式是
12、neednt,表示不必。 与neednt相当的动词形式是dont need to/dont have to/havent got to A: Must you leave soon? B: No, I neednt/dont need to/dont have to/havent got to. 必须：must与have to must侧重于说话人的主观意志 have to侧重客观需要 He must say it in English. (I want him to do so.) He have to say it in English. (He doesnt know Chinese.)
13、 在特定语境中，用will也可表示“义务”，常用于第二人称主语，这实际上是强化的祈使句。 You will wait outside the gate. Brian! You will close the door.,b)表示“必然”，可用should，ought to和must(一般用于陈述句)，其中must口气最为肯定。都指说话人根据一定情况做出推测或判断. She should be here in a minute These young trees ought to provide shade in ten years . All men must die. ought to(表示“
14、推测”）的否定形式是oughtnt to You oughtnt to have any difficulty getting the tickets.,如果是推测过去的事态，则用must +have done You must have left your handbag in the theatre. 表示推测的must的否定形式是cant不是must not If Fred didnt leave home before five, he cant be there yet.,4表示“预见”和“推测” a)表示“预见”，即表示“单纯将来”，可用will/shall+不定式，shall用于
15、第一人称，will用于第二、三人称。现在一般will可用于一切人称表“将来” I will be a different person when I live in England. You will be hearing from me. She will probably last longer than you will. It will rain tomorrow. 非正式语体中，will常用语第一人称主语表将来，常用will、shall的缩写ll，模糊了其界限。 Ill come in after church and give you a hand.,b)表示“推测”，除用shou
16、ld, ought to,和must外，还可用will/would（语气仅次于must）。 They should/ought to be home by now.(他们现在该到家了) They would be home by now.(他们现在大概到家了) They will be home by now.（我估计他们现在一定到家了） They must be home by now.（他们现在一定到家了）,will/would表示“推测”可有三种情况 1）对特定事态的推测 A: Whos that man over there? B: That will be George, no doubt. C: That would be George, I except. 2）对某些习惯性事态的推测，will指现在习 惯，would指过去习惯 He will work all day without a rest. Before his retirement he would catch the early bus every morning. 3）对某些不
