高中英语情态动词的用法一 can和could情态动词用法例句can/could表示能力1“I dont think Mike can type.” “Yes, he can.”2I can speak fluent English now , but I couldnt last year.在肯定句中，表示客观可能性，并不涉及具体某事会发生，常用来说明人或事物的特征（译为“有时会”）。要表达具体某事实际发生的可能性时，不用can，需用could，may，might。1 As a human being, anyone can make a mistake.2 Im confident that a solution can be found.3 He can be very forgetful sometimes.4 I may stay at home this weekend.（实际可能性）5 Peter might come to join us.(实际可能性) 6 It will be sunny in the daytime ,but it could rain tonight.(实际可能性)表示请求和允许。表示请求，口语中常用could代替can，使语气更委婉。1 Can we turn the air conditioner on?2 Any police officer can insist on seeing a drivers license.3 In soccer, you cant touch the ball with your hands.4 Could you have her call me back when she gets home, please?5 I wonder if I could just ask you to sign this.表示对现在的动作或状态进行主观的猜测，主要用在否定句和疑问句中。1 It cant be easy caring for a man and a child who are not your own.2 Can the man over there be our head master?表示惊异、怀疑、不相信等态度，主要用在否定句、疑问句和感叹句中。1 Can this be an excuse for not giving them help?2 This cant be true.3 How can you be so crazy.特别说明：（1） could用来表示请求时，语气委婉，主要用于疑问句，不能用于肯定句，答语应用can（即：could不能用于现在时态的简略答语中）。如：Could I use your dictionary?Yes, you can.(否定回答可用：No, Im afraid not.或者是you cant)表示推测时，could不是过去式，只是语气更委婉；若是推测已发生的事或过去的情况，用can/could have done(2) can和be able to辨析can(could)和be able to都可以表示能力，意思上没有区别。但can只有现在式和过去式，而be able to则有更多的形式。如：Ive always wanted to able to speak fluent English.Those bags look really heavy, are you sure youll be able to carry them on your own?但是，表示在过去某时的某一场合经过一番努力，终于做成了某事，通常不用could，而用was/were able to来表示。这时，was/were able to相当于managed to do或succeed in doing。如：After the accident it was a long time before she was able to walk again.The fire was very big, but most people were able to escape from the building.(3) 惯用形式“cannot too”表示“无论怎么也不（过分）”。如： You cannot be too careful.你越小心越好。 惯用形式“cannot but+ 不定式（不带to）”表示“不得不，只好”。如： I cannot but admire her determination.我不得不钦佩你的决心。 二may和 might情态动词用法例句may/might表示允许、许可。否定回答一般用must not/mustnt,表示“禁止、阻止”之意，但也可以用had better not (最好别)或may not（不可以），语气较为委婉。1 May I come in and wait?2 May I smoke here?No, you mustnt(或No, youd better not.)在表示请求、允许时，might比may语气更委婉些。用May I征询对方许可在文体上比较正式，在口气上比较客气，在日常用语中，用Can I征询对方意见更为常见。1 Might I borrow your pen?2 I wonder if I might speak to your son.表示可能性的推测，通常用在肯定句和否定句中，含有“或许”“大概”“可能”之意；用might代替may时，则语气显得更加不肯定。1 It may rain this afternoon.2 She might come to join us this afternoon.3 I suppose he might have missed the train.may用于祈使句表示祝愿1 May you succeed.2 May you live happily!3 May she rest in peace.愿她安息。惯用句式：“may as well或might(just)as well+动词原形”意为“最好，满可以，倒不如”，相当于“had better或there is no reason to do anything else.1 There is nothing to do, so I may as well go to bed.2 You may as well tell us now, well find out sooner or later.3 I suppose we might as well go home.4 And if you have to plough the field anyway, you might as well plant it at the same time.二must和have to情态动词用法例句must表示“必须，应该”之意，语气比should，ought to强烈。其否定形式mustnt表示“不准，不应该，禁止”等意1 You must come to school on time.2 Everybody must obey the law.3 You mustnt drive so fast in the street.4 We mustnt waste any more time.在回答带有must的问句时，否定回答常用neednt或dont have to，表示“不必”，而不用mustnt1Must I come back before ten? Yes，you must. -No, you neednt(No, you dont have to)表示有把握的推测，意为“一定、准是、相必”，只用于肯定句中1 It must be my mother.2 You must be hungry after a walk.3 There must be a hole in the wall. have to“必须，不得不”，意义与must相近。但must表示的是说话人的主观看法，而have to则往往强调客观需要。1 The film is not interesting. I really must go now.2 I have to go now, because my mother is in hospital.must只有一种形式，即现在式与过去式都是一种形式，而have to则涉及各种人称、时态等方面的变化形式。1I had to work hard when I was your age.2I will have to learn how to use a computer.3In order to take the exam, well have to finish the whole book by the end of this month .两者的否定意义不同，mustnt表示“禁止，不许”，dont have to表示不必。1 You mustnt go there.2 You dont have to go there.注意：表示”偏要，硬要做某事-how old are you, madam?-if you must know, Im twice my sons age(如果你非得知道，是我儿子年龄的两倍)四shall和should情态动词用法例句shall用于第一、三人称构成的疑问句，表示征求对方意见或请求指示,其意为“要不要”、“好吗”：1 Shall I open the window?2 Shall we say 6 oclock, then?3 Shall he come to see you?1 用于第二、三人称陈述句中，表示说话人给对方的命令、警告、允诺、威胁、命令、规定、必然性等2表示强制，用于法令、条约、规章中，意为“必须，应该”。1 Dont worry, you shall get the answer this afternoon.(允诺)2 He shall be sorry for it one day, I tell you. （警告）3 You shall do as I say. (命令)4 If you children dont do as I tell you, you shall not go to the party. (威胁) 5 The Persons under 18 shall not be employed in night work不满十八岁的人不得雇佣干夜间工作。(表规定) 6 That day shall come(表必然性)7 Candidates shall remain in their seats until all