情态动词的基本用法

1、情态动词的基本用法情态动词的特点没有人称和数的变化。有些情态动词有过去式的变化：will would , can could , may might , dare daredcan (could)表示能力。Two eyes can see more than one.表示允许。Can I have a look at your new pen?Can (Could) you lend me a hand?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 (couldn t) be over s

2、ixty.How can you be so careless?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 can t 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.表可能（事实上） 。 语气不肯定。He may be at home. 他可能在家。 She may not know

3、about it.I am afraid they might not agree with him.They might be having a meeting, but I m not sure.must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 needn t. / No, you don t have to.表示很有把握的推断，意为“想必、准是、一定”等，只用于肯定句。

4、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.shall表征询意见，用于第一、第三人称疑问句。Shall I get you some tea?have (has)to：Shall the boy wait outside?Its a fine day. Lets go fishing, shall we?表说话人的意愿，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

5、 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）will表意愿，用于各种人称陈述句。I will do anything for you.If you will read the book, I ll lend it to you.表请求，用于疑问句。Dont smoke in

6、 the meeting room, will you?Won t you drink some more coffee?表示某种倾向或习惯性动作。Fish will die out of water. The door won t open.would表意愿。They would not let him in because he was poorly dressed.表委婉地提出请求、建议或看法。Would you like another glass of beer?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 g

7、o to him for help.should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。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 actors.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 to意为“应该

8、” ，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。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 several 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

9、( 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/beHe 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. 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

10、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 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 a

11、bout 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 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

12、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 can t 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 can

13、t 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 can t have finished the work so soon.这项工作他不可能完成得这样快。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

14、，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：can t /couldn t/may not have been doingHe can t 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?Can it be true?他现在会在哪里呢？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 doingIt s so

15、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?Where can she have gone?她会不会说谎了？她会上哪儿去了呢？情态动词的辨析need 和 dare用作情态动词Need he go yesterday? 昨天他有去的必要吗?I don t think you need worry.She dare not go out alone at night.How dare

16、you say I m unfair?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 he ll come again.can 和 be able tobe able to 表示经过努力后, 能够做到 ; be able to 有多种形式的变化。can1.表示体力或脑力方面的能力;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。The fir

17、e spread through the hotel very quickly but everyone was able to get out. 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 her that she must give up smoking.We had to get everything ready that night.would 和 used to1） used to “过

18、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 can t / couldn t 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