1、情态动词的基本用法情态动词的特点1. 没有人称和数的变化。2. 有些情态动词有过去式的变化：will would , can could , may might , dare daredcan (could)1. 表示能力。 Two eyes can see more than one. 2. 表示允许。 Can I have a look at your new pen? Can (Could) you lend me a hand? 3. 表惊异、怀疑、不相信等态度。主要用于否定句、疑问句或感叹句中。Where can (could) they have gone to? He can t
2、 (couldnt) be over sixty. How can you be so careless? 4. 表示猜测 (肯定句把握较小；否定句几乎为 100%把握)The temperature can fall to 10. You cant be serious.may (might)1表允许，might 是 may 的过去式; 用在疑问中比 may 委婉、客气。You may take whatever you like. He told me that I might smoke in the room. 2. 表可能（事实上） 。 语气不肯定。He may be at home
3、. 他可能在家。She may not know about it. I am afraid they might not agree with him. They might be having a meeting, but Im not sure. must1. 表必须（主观意志）We must do everything we can to help him. You mustnt talk to her like that. -Must we hand in our exercise books now?-No, you neednt. / No, you dont have to.
4、2. 表示很有把握的推断，意为“想必、准是、一定 ”等，只用于肯定句。have (has)to：have (has)got to 必须 , 不得不。过去式为 had to。He must be ill. He looks so pale. She must have a lot of money, for she drives a BMW.shall1. 表征询意见，用于第一、第三人称疑问句。Shall I get you some tea? Shall the boy wait outside? Its a fine day. Lets go fishing, shall we?2. 表说话
5、人的意愿，有“命令、允诺、警告、决心”等意思，用于第二、第三人称陈述句。You shall do as I say. （命令）You shall have the English book as soon as I finish it.（允诺）He shall be sorry for it one day, I tell you. （警告）Everything that he owns shall be taken away from him.（决心）will1. 表意愿，用于各种人称陈述句。I will do anything for you. If you will read the b
6、ook, Ill lend it to you. 2. 表请求，用于疑问句。Dont smoke in the meeting room, will you? Wont you drink some more coffee? 3. 表示某种倾向或习惯性动作。Fish will die out of water. The door wont open. would1. 表意愿。They would not let him in because he was poorly dressed. 2. 表委婉地提出请求、建议或看法。Would you like another glass of beer
7、? 3. 表过去反复发生的动作或过去的一种倾向。Every time she was in trouble, she would go to him for help.should1. 表义务。意为“应该” ，用于各种人称。You should listen to the doctors advice. 你应该听从医生建议的。You should study the article carefully. 你应该仔细读那篇文章。2. 表推测，意为“想必一定、照说应该、估计”等。The film should be very good as it is starring first-class a
8、ctors. 那部电影想必很棒，都是一流的演员。They should be home by now. 现在他们应该已经到家了ought to1. 意为“应该” ，口气比 should 稍重。Ought you to smoke so much? 你应该抽这样多烟吗？ You ought to write to the mayor. 您应该给市长写信。 2. 表推测，暗含很大的可能。She ought to know his telephone number. 她应该知道他的电话号码。used to过去常常, 现在不复发生或存在。The Greeks used to worship sever
9、al gods. 过去,希腊人崇奉好几种神。 He used to smoke. 他过去抽烟（现在不抽了） 。情态动词的推测用法 肯定句中：must (一定)，may (可能)，might/could (也许，或许) 其语气的肯定程度依次递减。其中，might 和 could 并非过去时态，只是语气较为委婉或可能性较小 对当前行为、情况或状态的推测：must /may /might /could + do/be He must/may/might/could be in the reading room. 他肯定/可能/也许在阅览室里。I must look funny in this hat
10、. 我戴这顶帽子看起来一定很滑稽。 对此时此刻正在进行的动作的推测：must /may/ might/ could + be doing 想必/ 可能正在 He must /may/ might/ could be watching TV at this time.他此时一定/可能/或许在看电视。They must be waiting for us. 他们肯定在等着我们。 对过去发生的事情的推测：must /may /might /could + have +过去分词 想必/可能已经They must have arrived by now. 现在他们肯定已到了。You look very
11、tired. You must have stayed up last night.看上去你很疲劳，你昨晚一定熬夜了。You may have read about it in the papers. 你可能在报上已读到这件事了。 过去的一段时间内一直在进行的动作：must/may /might/ could + have + been +doing 想必/可能一直在They are sweating all over. They must have been working in the fields.他们浑身是汗，准是在地里劳动来着。He may have been waiting for
12、 us for an hour. 他可能等我们一小时了。2否定句中：can/could not 不可能，想必不会may/might not 可能不对当前行为、情况或状态的推测：can/could not+动词原形 不可能，想必不会may/might not +动词原形 可能不He may not be busy now. 也许他现在不忙。He can not be busy now. 他现在一定不忙。He cant be in the reading room. I saw him on the playground just now.他不可能在阅览室里，我刚看到他在操场上。对此时此刻正在进行
13、的动作的推测：can/could not + be doing 不可能，想必不会在干某事may/might not + be doing 可能没在干某事They cant be telling the truth. 他们不可能在说真话。They may not be telling the truth. 他们可能没在说真话。对过去发生的事情的推测：can/could not + have +过去分词 不可能，想必不会做过某事may/might not + have +过去分词 可能没干过某事He cant have finished the work so soon. 这项工作他不可能完成得这
14、样快。He may not have achieved all his aims. But his effort is a good one.他可能没达到他的全部目的，但他还是认真做了努力的。过去的一段时间内一直在进行的动作：cant /couldnt/may not have been doing He cant have been waiting for us so long. 他不可能等我们那么长时间。3疑问句中：常用 can/could 来表示说话人的猜疑、怀疑或不肯定的语气 对当前行为、情况或状态的推测：can/could + 主语+ do/beWhere can he be now
15、? 他现在会在哪里呢？Can it be true? 那会是真的吗？ 对此时此刻正在进行的动作的推测：can/could +主语+ be doingIts so late. Can Tom be reading? 这么晚了，汤姆还在看书吗？What can he be doing? 他可能在做什么呢？ 对过去发生的事情的推测：can/could +主语+have doneCan she have told a lie? 她会不会说谎了？Where can she have gone? 她会上哪儿去了呢？情态动词的辨析need 和 dare1. 用作情态动词Need he go yesterda
16、y? 昨天他有去的必要吗? I dont think you need worry. She dare not go out alone at night. How dare you say I m unfair?2. 用作实义动词She needs the work done before tomorrow. 她必须在明天以前找人完成这项工作。The table needs painting (to be painted.). I dare say hell come again. can 和 be able tobe able to 表示经过努力后, 能够做到; be able to 有多
17、种形式的变化。can 1.表示体力或脑力方面的能力; 2. 表示允许、可能性。could 是 can 的过去式, 表示过去有能力及过去存在的可能性；用于疑问句表示委婉地提出问题。1. The fire spread through the hotel very quickly but everyone was able to get out. 2. Will you stay for lunch? Sorry, I cant. My brother is coming to see me. must 和 have tomust 表示主观意志，而 have to 表示由于客观因素。I told
18、her that she must give up smoking. We had to get everything ready that night.would 和 used to1）used to “过去常常”, 与现在事实相反; would 表过去意愿。People used to think that the earth was flat.She would go out for a walk in the morning when she was in the country. 易错点点拨：1情态动词无论是表达“推测和可能性” ，还是表达“虚拟”这一概念，只要是对过去已经发生的事情
19、进行描述，一律用“情态动词+have done”这一结构；对现在或将来的事情进行描述，用“情态动词+动词或系动词原形” 。2should (not) / ought (not) to 在中表示根据常规或常识推测，表示“某事应该或不应该发生” ，语气比 must 或 cant / couldnt 稍弱。3. can, could 表达推测时，一般用于疑问句和否定句中；can 用于肯定句中表示一种理论上的可能性，并不牵涉是否真的会发生，在这种用法中 can 只能与动词原形连用； could 用于肯定句中，语气比may/ might 更弱。4. must 表达 “情感、态度、语气 ”主要有以下用法：
20、(1) 表示主观的义务和必要，主要用于肯定句和疑问句，意思为“必须，得，要” ；由must 引起的疑问句，肯定回答要用 must 或 have to， 否定回答要用 neednt 或dont have to,意思是“不必” 。另外，must 与 have to 都可以表示“必须”这一含义。must 表示一种主观的需要，而 have to 表示一种客观的需要，意思是 “不得不 ”，其否定形式是 don have to。(2) must 用于条件句或疑问句中，可以用来表示责备、抱怨的感情色彩，意思为“偏要，硬要、干嘛” 。5. 在虚拟条件句中用以加强假设语气，表示“与将来事实相反的假设” ，用 If+主语+ should +动词原形，当“万一(会)”讲。这时可省略 if，将 should 提到句首，变为倒装句式。If it should rain(=Should it rain) tomorrow, I would stay at home.万一明天下雨的话，我就待在家里。6. should 还可以用来表示说话人对某事不能理解、赶到意外、惊异等意思，译为“竟然，竟会” 。You cant imagine that a well-behaved gentleman should be so rude to a lady.
