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课件网) UNIT 5 THE VALUE OF MONEY Discovering Useful Structures Definition of modal verbs 一、情态动词的特征 情态动词有一定的意义，表示或暗示某种情绪或态度，表示可能、建议、愿望、必要、允许、能力等。 大多数情态动词有多个意义。 2. 情态动词没有人称和数的变化，即不随主语的不同而变化。 3. 情态动词不能独立使用，须后接动词原形，一起构成谓语动词。 4. 情态动词除ought和have外，后面接不带to的不定式。(dare) 5.情态动词没有非谓语形式，即没有不定式、分词等形式。 Classification of modal verbs 1.只作情态动词的： 2. 可情态可实义的： 3. 可情态可助动词的: 4. 相当于情态动词的: can/could, may/might, ought to, must need, dare shall/should, will/would have to, used to Functions of modal verbs Summary: 情态动词可用来表示需要、可能性、委婉请求、推测、愿望、建议、义务、意愿、禁止等。 You have to read between the lines because the real messages are often hidden… It may seem lucky to you. Astronauts must wear spacesuits when they work in space because… May we ask what you’re doing in this country You’d better not open it. What would you do if you were in her situation Oliver believes that with a million-pound bank note a man could live a month in London. necessity 表必要性 possibility 表可能和推测 obligation 表义务性 request 表征求许可 intention 表意图和愿望 A. necessity B. possibility C. obligation D. request E. advice F. intention advice 表建议 ability 表能够 Modal verbs possibility necessity obligation request advice intention can(could更委婉) may(might更委婉) need have to(客观) /must (主观) must/ought to would may should/ought to had better would must can Functions The man can/could speak two foreign languages. —Can I use your phone —Of course you can. It can be very hot here in summer. It can’t be the headmaster. He has gone to America. can / could 用法 说明 1.表示能力 could是can的过去式，表示有能力做或能够发生，意为“会，能，能够” 2.表示请求和允许 could语气更委婉，肯定回答时要用can，不用could 3.表示理论上的 可能性 表示“有时会”，用于肯定句中 4.表示推测 表示“可能”，用于否定句和疑问句 —May I have a look at your book —Yes, you may/can. No, you mustn't/can't He may/might not be at home at this time. May God bless you. 用法 说明 1.表示请求和许可 意为“可以”。在疑问句中,might可以代替may,语气更加委婉。给予许可时用may或can, 否定回答时要用mustn't或can't 2.表示推测 意为“可能”。通常用于肯定句和否定句中。may的可能性大于might，might语气更委婉 3.表示祝愿、希望 用于祈使句，只用may不用might，一般结构为 “may+主语+动词原形” may/might You must hurry up or you’ll be late. —Must I be home before eight o’clock —Yes, you must./No, you needn’t. He must be ill. He looks very pale and drawn. If you must go, at least wait until the storm is over. I can’t see things clearly. I have to wear glasses. must / have to 用法 说明 must表示义务 意为“必须”，强调说话人的主观看法,在回答带有must的问句时,否定式常用needn’t或don’t have to, 意为“不必”。 must表示推测 表示非常有把握的推测，意为“一定”,只能用在肯定句中。 must表 ... ...
