情态动词的用法

一． can和could

情态动词 can/could 用法 表示能力 例子 补充说明 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。要表达具体某事实际发生的可能性时，不用can，需用could，may，might。 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。 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。 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。 Can表现在能力；Could表示过1．I can speak fluent English now, 去能力.可用be able to代but I couldn’t last year. 替；was/were able to 表示成功做了某事 1. I may stay at home this 1. can用于否定和疑问句(couldweekend.（实际可能性） 不限) 2. Peter might come to join us.(实2. can (be)表示有时候会（常与 际可能性) sometimes, at times 连用） 3. It will be sunny in the daytime ,but it could rain tonight.(实际可能性) 1．Can we turn the air conditioner 1. 请求用could 语气委婉 on? 2. 允许不用 could. . 2. I wonder if I could just ask you to sign this. 1．It can’t be easy caring for a man and a child who are not your own. 2．Can the man over there be our head master? 1．Can this be an excuse for not giving them help? 2．This can’t be true. 3．How can you be so crazy! 特别提示：

（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，回答应该用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, I’m afraid not.) (2) can和be able to区分

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：

I’ve always wanted to able to speak fluent English.

Those bags look really heavy, are you sure you’ll 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 may/might 用法 例子 补充说明 表示允许、许可。否定回答一般用must 1． May I come in and wait? 1. 请求用might语气更委not/mustn’t,表示“禁止、阻止”之意，2． ——May I smoke here? 婉。 但也可以用had better not (最好别)——No, you mustn’t(或No, 2. 允许时用may，表示“可you’d better not.) 或may not（不可以），语气较为委婉。 以”（表示允许时不用might）。 在表示请求、允许时，might比may语气1． Might I borrow your pen? 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。 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1． It may rain this afternoon. 否定句中，含有“或许”“大概”“可能”2． I suppose he might have missed the train. 之意；用might代替may时，则语气显得更加不肯定。 may用于祈使句表示祝愿 1． May you succeed！ 常用于肯定句（might可能最小） 惯用句式： 1． There is nothing to do, so I may as well go to bed. “may well+ 动词原形”，意为“完全能，很可能”，相当于to be very likely to 2． You may as well tell us now, we’ll find out sooner or later. “may as well或might(just)as well+3． I suppose we might as well go home. 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.

二．must和have to 情态动词 Must 用法 例子 补充说明 表示“必须，应该”之意，语气比1． You must come to school on time. 1. must多表主观、现在/将来should，ought to强烈。其否定形式2． You mustn’t drive so fast in the 义务; have to多表客观、street. mustn’t表示“不准，不应该，禁止”过去义务

等意 3． We mustn’t waste any more time. 2. mustn't表\禁止\；否定用needn't / don't have to have to 在回答带有must的问句时，否定1．—Must I come back before ten? 回答常用needn’t或don’t have to， —Yes，you must.(No, you needn’t) 表示“不必”，而不用mustn’t 表示有把握的推测，意为“一定、1． It must be my mother. 只用肯定句。在否定句/疑问句准是” 中用can/could 2． You must be hungry after a walk. 3． There must be a hole in the wall. “必须，不得不”，意义与must相1． The film is not interesting. I really must go now. 近。但must表示的是说话人的主观看法，而have to则往往强调客2． I have to go now, because my mother is in hospital. 观需要。 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。 两者的否定意义不同，mustn’t表示“禁止，不许”，don’t have to表示不必。 1．I had to work hard when I was your age. 2．In order to take the exam, we’ll have to finish the whole book by the end of this month. 1． You mustn’t go there. 2． You don’t have to go there. 3．

四．shall和should

情态动用法 词 shall 用于第一、二、三人称构成的疑问句，表示征求对方意见或请求指示 用于第二、三人称陈述句中，表示说话人给对方的命令、警告、允诺或威胁。 例句 1． Shall I open the window? 2． Shall we say 6 o’clock, then? 3． What shall I get for dinner? 补充说明 “必须”1． Don’t worry, you shall get the 表规章、法令、预言：用于所有人称 Every answer this afternoon.(允诺) 2． He shall be sorry for it one day, I competitor shall wear a number tell you. （警告） 3． You shall do as I say. (命令) 4． If you children don’t do as I tell you, you shall not go to the party. (威胁) should 表示劝告或建议，意为“应该” 1． What should I do? 2． Should I trust him? 3． You should read his new book. 表示推测，用在肯定句中，对现在的情况或可能发生 的事的主观推测或期待。意为“想必，大概，或许” 1． It should be a nice day tomorrow. 肯定的语气没有must用于推测2． Try phoning Robert, he should be 时强 This pen ought to /should home now. be yours. 3． He should be around sixty years

old. 还可以用在if引导的条件句中，表示一件事听起来可能性很小，但也不是完全不可能，相当于“万一”的意思。从句谓语用should+动词原形构成，主句都一定用虚拟语气 1． Ask Tom to ring me up if you should see him. (你万一见到汤姆，请让他给我打个电话) 2． Should I be free tomorrow, I’ll come. (万一我明天有时间，我就过来) 3． If things should change suddenly, please let me know. (万一情况突变，请通知我) 用于疑问句或感叹句中，表示意1． Why should anyone want to marry Tony? 外、惊异的情绪，意为“竟会”，与why，what，how，who连用，2． Don’t ask me. How should I know? 如果是疑问句，则不需要回答。

五．will和would

情态动词 will/would 用法 用于表示意志或意愿。will指现在，would指过去。 例句 补充说明 无意义1． He is the man who will go his own Would此时为will过去式，way. (他是个自行其是的人。) 差别 2． They said they would meet us at 10:30 at the station. 表示请求、建议等，用would比用will委婉、客气。 1． Will you please take a message for 此意用于疑问句，常与you连用 him? Will you give me a piece of paper? 2． Would you please tell me your telephone number? 表示习惯或倾向，意为“总是，惯于”。will至现在，would指过去。 Would表过去反复的动作/某种倾1． Fish will die without water. 2． People will talk. (人们总会说闲向(相对于used to无“现已无此习话。) 惯”之义。) 3． When we worked in the same office, we would often have coffee together. 1． These things will happen. 2． That will be the messenger ringing. 3． It would be about ten o’clock when he left home. 此意表对目前事物的预料。That will be the postman ringing.(would表示过去/现在；will表示现在/将来) 叙述真理：The tree will leave without water for 3 months. 表示推测，意为“很可能，大概”。will表示推测比should把握大，比must把握小。 表示功能，意为“能，行”。1． That will be all right. 惯用形式：will do/would do2． Either pen will do. 表示“解决问题”、“就行”。 3． It would not do to work too late.（工作太晚不行。） 用于否定句中，意为“不肯”、1．I won’t listen to your nonsense. “不乐意” 2．No matter what I said, he wouldn’t listen to me.