2023届高考英语语法专项：情态动词汇总讲义学案（含答案）
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| 名称 | 2023届高考英语语法专项：情态动词汇总讲义学案（含答案） |  | |
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| 更新时间 | 2022-11-23 21:57:05 | ||
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情态动词
情态动词的用法：
常用的情态动词有can，may，must，need,should, had better.
1. can 的用法：
① 表示能力 “能，会” eg: He can speak a little Japanese.他会说一点日语。
② 表示请求或许可 “可以” eg: Can I help you 要我帮忙吗
③ 表示猜测 “可能” eg: Where can she go now 她可能到哪里去了呢
2.may 的用法：
①表示请求或允许 “可以”“准许” eg: May I go home，please 请问我可以回家吗
② 表示可能性 “ 可能”、也许” eg: I think it may rain this afternoon. 我想今天下午可能下雨。
注：might为may的过去式，但也可以代替may，语气较为婉转客气或更加不肯定。
eg: ① He might not come today.今天他也许不来了。(语气不肯定)
②You might also get a headache when you work too hard，当你工作太努力时，你也可能患头痛
3. must的用法：
①表示义务、必要或命令 “必须、应该” eg: You must come early tomorrow．你明天得早来。
② 表示推测时“肯定，一定” eg: They must be at home.The light is on 他们肯定在家,灯亮着呢.
③ must not 禁止，不许 eg: You must not tell lies. 你不许撒谎。
注意： ①must开头的疑问句，其否定回答通常用 don't have to 或needn't 。而不用mustn't
eg: ---Must I finish my homework first 我必须先完成作业吗？
---No, you don't have to/ needn't. 不，你不必。
② can 和 must在 表推测时，can一般否定句中，而must 常用于肯定句中。
eg: ①It can not be Li Lei 那个人不可能是李磊
② It must be Li Lei 那个人肯定是李磊。
4. need 的用法：
① 情态动词 “需要, 有必要”一般用于否定句或疑问句中。
eg: You needn't come here this afternoon.你今天下午不必来。
② 行为动词 “需要, 有必要” 可以用于各种句式中。
eg: ①You don't need to go now. 你不必现在就走。
② I need to have a rest. 我需要休息一下
③ Do we need to finish all the work today 我们今天需要完成所有的工作吗？
need的用法的助记口诀：
实义动词表“需要”，后接名、代、不定式。 need后接动名词，主动形式表被动。
情态动词表“需要”，没有人称 数之变。 其后直接加动原，多用疑问与否定。
5.征求许可或给予许可，“我可以···？”用句型“Can/May/Could/Might I... ”其中"Can I... "属于非正式用法，
"May I ... "属于正式用法。"Could/Might I... "的回答通常不用could或might，而用may或can或其他表示客
气的词语。
6.肯定句中表推测“可能”：can,could,may,might都可以在肯定句中表“可能”。其中can的语气最强，可能性
最大，其余依次递减。 肯定句中表推测“一定，肯定”用must.
7.疑问句中表推测“可能”：用can,could,might,而不能用may. mustn't 不表示推测，而表示禁止。
意义为“禁止，不准”
8.否定句中表推测： may not/might not：可能不 can not/could not： 不可能
eg: ①You may not be right．你也许不对. ② You can not be right．你不可能对.
9.以may（表许可或请求）开头的一般疑问句的肯定回答用may，否定回答用mustn't或can't。
10.表示“必须”时，must表示主观看法，have to强调客观需要。
11.ought to和should两者都表示应该，但是ought to比should语气强。
12.would rather与than连用，其结构是：would rather...than...或would...rather than...。would(rather)和than后面
都接动词原形，如果用的动词相同，则than后省去该动词。would rather...than...的意义为“宁愿···而不是···”
eg:I would rather play football than baseball.我宁愿踢足球而不愿打棒球。
13. 情态动词的助记口诀：
情态动词两要点：动词原形跟后边 没有人称 、数之变
can 表能力 may许可 must来把责任担（必须） 否定回答need换。
need需要 dare敢 should应该 would like 愿(意) have to“ 不得不”表客观。
14.had better用法的助记口诀：
表示“建议”和“忠告”，had better 为最好。 建议某人“最好不···”，要用 had better not do。
情态动词的用法要点
can和could
情态动词 用法 例句
can/could 表示能力 1．“I don’t think Mike can type.” “Yes, he can.”2．I can speak fluent English now , but I couldn’t 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。要表达具体某事实际发生的可能性时，不用can，需用could，may，might。 As a human being, anyone can make a mistake.I’m confident that a solution can be found.He can be very forgetful sometimes.I may stay at home this weekend.（实际可能性）Peter might come to join us.(实际可能性) 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。 Can we turn the air conditioner on Any police officer can insist on seeing a driver’s license.In soccer, you can’t touch the ball with your hands.Could you have her call me back when she gets home, please 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。 It can’t be easy caring for a man and a child who are not your own.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。 Can this be an excuse for not giving them help This can’t be true.How can you be so crazy.
特别说明：
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, I’m afraid not.)
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：
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 用法 例句
may/might 表示允许、许可。否定回答一般用must not/mustn’t,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。 May I come in and wait ——May I smoke here ——No, you mustn’t(或No, you’d 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。 Might I borrow your pen 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。 It may rain this afternoon.She might come to join us this afternoon.I suppose he might have missed the train.
may用于祈使句表示祝愿 May you succeed.Long may he live! 愿他能持续住下去。May you have many more days as happy as this one.May she rest in peace.愿她安息。
惯用句式：“may well+ 动词原形”，意为“完全能，很可能”，相当于to be very likely to“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. It may well change forever the way you look at Greek art.There may well be a real problem here.There is nothing to do, so I may as well go to bed.You may as well tell us now, we’ll find out sooner or later.I suppose we might as well go home.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mustn’t表示“不准，不应该，禁止”等意 You must come to school on time.Everybody must obey the law.You mustn’t drive so fast in the street.We mustn’t waste any more time.
在回答带有must的问句时，否定回答常用needn’t或don’t have to，表示“不必”，而不用mustn’t 1．—Must I come back before ten —Yes，you must.(No, you needn’t)
表示有把握的推测，意为“一定、准是、相必”，只用于肯定句中 It must be my mother.You must be hungry after a walk.There must be a hole in the wall.
have tohave 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。 The film is not interesting. I really must go now.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。 1．I had to work hard when I was your age.2．I will have to learn how to use a computer.3．In order to take the exam, we’ll have to finish the whole book by the end of this month .
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。 You mustn’t go there.You don’t have to go there.
补：
情态动词can、may、must的横向辨析
一、表示“能力”。
l．只可用can（could）。may、must则无此种含义。
例：①I can swim now，but I couldn’t last year.
②Can you play me piano？Yes，I can．
2．can（could）适用于各种句型和人称。
例：①肯定句：I（You，He）can swim.
②否定句：I（You，He）can’t swim.
③疑问句：Can I（you，he）swim？
二、表示“请求”或“许可”。can、may、must都可用，但语气和程度不同。
1．can（could）用于各种句型和大部分人称。
例：①肯定句：You（He，We）can go now．
②否定句：You（He，We）can’t go now．
③疑问句：Can I（you，he）go now？
Yes，you can．（No，you can’t．）
2．may（might）用于各种句型，但在肯定句和否定句中不用于第一人称；在疑问句中不用于第二人称。
例：①肯定句：You（He）may go now．
②否定句：You（He）may not go now．
③疑问句：May I（he）go now？
正规回答：（表定）Yes，you may．
（否定）No，you may not．（No，you can’t．／No，you mustn’t．）
口语化回答：（肯定）Yes，please．（Certainly．）
（否定）No，please don’t．（No，of course not．）
3．must用于各种句型和大部分人称。
例：①肯定句：I（You，He）must go now．
②否定句：You（He）mustn’t go now．
③疑问句：Must（you，he）go now？
肯定回答：Yes，you must.
否定回答：No，you needn’t．（No，you don’t have to．）
4．试比较：
You may not smoke here．（不可以）语气轻
You can’t smoke here．（不能）重
You mustn’t smoke here．（决不可）最重
三、表示“可能”、“或许”和“推测”之意。can、may、must都可用，但语气和程度不同。
l．can （could）常用于否定句和疑问句中，could表示的“可能性”更小。
例：①否定句：It couldn’t be him，for he’s at the library．
②疑问句：Can he have gone out？
What can they be doing now？
2．may（might）用于肯定句和否定句中，might表示的“可能性”更小。
例：①肯定句：He may be right．
②否定句：She might not have come yet．
3．must用于肯定句中。
例：①You must be very hungry．（对现在情况猜测）
②Aqiao must have met a fairy．（对过去事实的猜测）
③Everything is clean and tidy．Someone must have cleaned my room．（同上）
4．试比较：
He might not have gone out．（或许没有）
He can’t have gone out．（不可能）
He must have been in the room．（一定、准是）
以上三句可能性逐渐加大至肯定。
练习题：
一、说明下列句中情态动词的含义。（A．能力；B．许可；C．猜测）。
（ ） l. “You must write more neatly,” said the teacher．
（ ） 2. He’s not in the office．He must have gone to the meeting．
（ ） 3. Visitors mustn’t move and touch the exhibits．
（ ） 4. The girl can play the violin very well．
（ ） 5. Can I smoke here？
二、用can（could），may（might），must填充。
1. When I was young，I_____ run very fast．
2. What _____ I do for you，Li Hat？
3. I wonder where Ann is．She _________ be with Dick，I think．
4. A：That pen _______ be his．
B：No，it _______（not）be his．
5. Could I use your phone？Yes，of course you _________.
四．shall和should
情态动词 用法 例句
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 Shall I open the window Shall we say 6 o’clock, then What shall I get for dinner
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。 Don’t worry, you shall get the answer this afternoon.(允诺)He shall be sorry for it one day, I tell you. （警告）You shall do as I say. (命令)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” What should I do Should I trust him 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” It should be a nice day tomorrow.Try phoning Robert, he should be home now.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 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)Should I be free tomorrow, I’ll come. (万一我明天有时间，我就过来)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，表示意外、惊异的情绪，意为“竟会”，与why，what，how，who连用，如果是疑问句，则不需要回答。 Why should anyone want to marry Tony Don’t ask me. How should I know
五．will和would
情态动词 用法 例句
will/would 用于表示意志或意愿。will指现在，would指过去。 He is the man who will go his own way. (他首歌自行其是的人。)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。 Will you please take a message for him 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。 Fish will die without water.People will talk. (人们总会说闲话。)When we worked in the same office, we would often have coffee together.
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。 These things will happen.That will be the messenger ringing.It would be about ten o’clock when he left home.
表示功能，意为“能，行”。惯用形式：will do/would do表示“解决问题”、“就行”。 That will be all right.Either pen will do.It would not do to work too late.（工作太晚不行。）
用于否定句中，意为“不肯”、“不乐意” 1．I won’t listen to your nonsense.2．No matter what I said, he wouldn’t listen to me.
特别说明：would与used to辨析
would可用来表示过去反复出现的动作，但不能表示过去存在的状态，所以我们不能说：“she would be a quiet girl.”
另外，would强调过去某种特定情况下的活动，是完全过去的事情，同现在没有联系。而used to则着眼于过去和现在的对比，隐含现在已不存在，动作或状态都可表示。Would可以表示不规则的习惯，used to则不可。如：
He used to be a naughty boy and cause trouble.
I used to get up at six in the morning.
Sometimes she would take a walk in the neighboring woods.
In those days, whenever I had difficulties, I would go to Mr. Chen for help.
六．need和dare
情态动词 用法 例句
need 用于表示“需要，必要”之意。做情态动词时，仅用于否定句和疑问句，只有现在时，过去式要用needn't have，疑问式用need+人称 ,否定式用need not(即needn't）， 1．—Need we leave soon —Yes, you must.(No, you needn't)2．You needn't have hurried.(=It was not necessary for you to hurry，but you did).你当时不必这么匆忙。
做实义动词时，其变化与一般的实义动词相同，后接带to的不定式（need doing = need to be done ）,过去式用needed、did you need 和didn't need,肯定式用needs/needed/need,疑问式用do、does、did提问，否定式要在前面加don't、doesn't、didn't 1. A job like nursing needs patience and understanding.(need+名词，need understanding=need to be understood,需要被理解)2．He needs to see a doctor.(need to do)3．Do you still need volunteers to help clean up after the party (need somebody to do something) 4．They didn't need to start so early.(do not need to do)
dare 用于表示“敢于”之意。做情态动词，没有人称和数的变化，主要用于否定句、疑问句和条件状语从句中 1．—Dare you tell her the truth —Yes, I dare. /No, I daren’t.How dare you accuse me of lying!He daren’t admit this.
用作实义动词时，其变化与一般的实义动词相同。在肯定句中，dare后接带to的不定式；否定句中，dare后既可接带to的不定式，也可接不带to的不定式。 Only a few journalists dared to cover the story.He doesn’t dare (to) go there alone.Don’t you dare (to) touch it
七．ought的用法：
情态动词 用法 例句
ought to do 表示“应该”之意 You ought to take care of him.—Ought I go now —Yes, you ought to. /No, you oughtn’t to.
表示推测。注意与must表示推测是的区别 He must be home by now. (断定他已到家)He ought to be home by now. (不十分肯定)This is where the oil must be. (比较直率)This is where the oil ought to be. (比较含蓄)
说明：should与ought to 表示“应该”时的区别
should 表示自己的主观看法，而ought to的语气中，含有“按道理应该……”之意。若要反映客观情况或涉及法律义务和规定，一般用ought to。如：
You should help them with their work.
You are his father. You ought to get him to receive good education.
八．“情态动词+have done”用法
情态动词+have done 用法 例句
must have done 表示主观上对过去已经发生的行为进行推测，意为“想必，准是，一定做了某事” She must have gone through a lot.He must have visited the White House during his stay in the United States.
may/might have done 表示对过去已发生行为的推测，意为“也许/或许已经（没有）……“。一般用于肯定句或否定句中，不用于疑问句。用might则表示语气更加不肯定。 You may have learnt the news.He may not have heard his name called.Sorry I’m late. I might have turned off the alarm clock and gone back to sleep again.
can…have donecannot have done 表示对过去发生的行为的怀疑和不肯定，通常用在否定句和疑问句中。（can换成could时语气委婉） Where can she have gone Could he have done such a foolish thing The boy can’t have finished reading the book so soon because it is difficult even to an adult.
could have done 可用于肯定句中，表示“可能已经……”之意，此外，还可以表示过去能做而没做的事，有一种对过去为付诸实施的事情的惋惜。 He could have killed himself driving at a dangerous speed.You could have been more considerate.You could have done better, but you were too careless.
might have done 表示“本来可能……，但实际上没有发生的事情”。另外，还可以表示“本来应该或可以做某事”之意，含有轻微的责备语气。 You should not swum in that sea. You might have been eaten by a shark.He might have given him more help, thought he was busy.
should/ought to have done 用于肯定句时，表示本该做某事，而实际上未做；用于否定句时，则表示不该做的事反而做了。 He should have known that the police would never allow this sort of thing.You shouldn’t have done it so carelessly.You ought to have returned the book earlier.You ought not to have refused his offer.
needn’t have done 表示做了本来不必去做的事。注意：didn’t need to do表示“没必要做而实际上也没有做某事” You needn’t have watered the plants, for it is going to rain.I didn’t need to buy the dictionary. I had a copy at home.
had better have done 用于事后的建议，含轻微责备的口吻，意为“当时最好做了某事”，其否定式had better not have done表示相反的含义。 You had better have started earlier.You had better not have scolded her.
would rather have done 表示“当时宁愿做了某事”，其否定式would rather not have done表示相反的含义，两者都表示“后悔”之意。 1．I would rather have taken his advice.2．I would rather not have told him the truth.
补：
can和could的用法
1. 表示能力或客观可能性，还可以表示请求和允许。如：
Can you finish this work tonight
你今晚能完成这项工作吗？
Man can not live without air.
人离了空气不能活。
— Can I go now — Yes, you can.
—我现在可以走了吗？—你可以。
注意：①could也可表示请求，语气委婉，主要用于疑问句，不可用于肯定句，答语应用can（即could不能用于现在时态的简略答语中）。如：
Could I come to see you tomorrow
我明天能来看您吗？
Yes, you can. （否定答语可用No, I'm afraid not.）
是的，你可以。（不，恐怕不行。）
②can表示能力时，还可用be able to代替。如：
I'll not be able to come this afternoon.
我今下午不能来。
2. 表示惊异、怀疑、不相信的态度。（主要用在否定句、疑问句或惊叹句中）
Can this be true
这可能是真的吗？
How can you be so careless!
你怎么能这么粗心！
This can not be done by him.
这不可能是他做的。
3. “can(could) + have + 过去分词”的疑问或否定形式表示对过去发生的行为怀疑或不肯定。如：
He can not have been to that town.
他不可能去过那个镇。
Can he have got the book
他可能拥有这本书吗？
4. 用在疑问句及否定句中,表示惊讶,不相信等.
5. can not```too\enough表示"无论怎样``````也不过分","越``````越好"
6.can 可以表示体力活脑力方面的能力，能够，能，会
Can you finish the work in such a short time
你能在那么短的时间内完成这项工作吗？
7. can 表示许可、允许 ， 在疑问句中表示要求，在否定句中表示不许，此时可以和may通用。
may和might的用法
1. 表示许可。
表示请求、允许时，might比may的语气更委婉一些，否定回答时(口语中常用) no , you can't . or , yes, please 用mustn't表示“不可以”、“禁止”、“阻止”之意(具有强烈禁止的意思)如：
You may drive the car.
你可以开这辆车。
— Might I use your pen — No, you mustn't.
—我可以用你的钢笔吗？—不，绝对不行。
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。在日常口语中，用Can I ... 征询对方意见在现代口语中更为常见。
2. 用于祈使句 ( http: / / baike. / view / 46257.htm" \t "_blank )中表示祝愿。如：
May you succeed!
祝你成功！
3. 表示推测、可能（疑问句不能用于此意）。
He may be very busy now.
他现在可能非常忙。
4. “may(might) + have + 过去分词”表示对过去发生的行为的推测。如：
He may not have finished the work.
他可能没有完成工作。
must和have to的用法
1. 表示必须、必要。（must表示主观多一些而have to则表示客观多一些）如：
You must come in time.
你必须及时过来。
回答must引出的问句时，如果是否定的回答，不能用mustn't，而要用needn't或don't have to。
— Must we hand in our exercise books today
— Yes, you must. (No, you don’t have to.)
—我们今天必须交上练习册吗？
—是的。（不，不必。）
2. “must be + 表语”的结构表示推测，它的否定或疑问式用can代替must。
This must be your pen.
这一定是你的钢笔。
3. “must + have + 过去分词”的结构常用在肯定句中，表示对过去发生的行为的推测。它的否定或疑问式用can代替must。
He must have been to Shanghai.
他一定去过上海。
4. have to的含义与must相似，两者往往可以互换使用，但have to有各种形式，随have的变化而定。must与have to有下列几点不同：
① 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。如：
The play is not interesting. I really must go now.
这部剧没意思。我真的必须现在就走。
I had to work when I was your age.
当我像你这么大时，我不得不工作。
② must一般只表现在，have则有更多的时态形式。
③ 二者的否定意义不大相同。如：
You mustn't go. 你可不要去。
You don't have to go. 你不必去。
④ 询问对方的意愿时应用must。如：
Must I clean all the room
我一定要打扫整个房间吗？
注意：have to也可拼做have got to。
5. 表示一种与说话人 愿望相反、不耐烦的感彩，偏偏、非要。
Why must you always bother me
为什么你总是来烦我？
dare和need的用法
1. need表示“需要”或“必须”，作情态动词时，仅用于否定句或疑问句中，在肯定句中一般用must, have to, ought to,或should代替。如：
You needn’t come so early.
— Need I finish the work today
— Yes, you must.
注意：needn't + 不定式的完成式“表示本来不必做某事而实际上做了某事”。如：
You needn't have waited for me.
2. Dare作情态动词时，主要用于疑问句、否定句和条件从句 ( http: / / baike. / view / 2066094.htm" \t "_blank )中，一般不用在肯定句中。如：
How dare you say I'm unfair.
He daren't speak English before such a crowd, dare he
3. Dare和need常用作实义动词，有时态、人称和数的变化，所不同的是，作实义动词时，在肯定句中，dare后面通常接带to的不定式，在否定和疑问句中，dare后面可接带to或不带to的不定式。如：
I dare to swim across this river.
He does not dare (to) answer.
Don't you dare (to) touch it!
I wondered he dare (to) say that.
He needs to finish it this evening.
shall和should的用法
一.Shall的用法：
1. Shall用于第一人称，表示征求对方的意愿。如：
What shall we do this evening
2. Shall用于第一、第三人称疑问句中，表示说话人征求对方的意见或向对方请示。如：
Shall we begin our lesson
When shall he be able to leave the hospital
3. Shall用于第二、第三人称，表示说话人给对方命令、警告、允诺或威胁。如：
You shall fail if you don't work harder. （警告）
He shall have the book when I finish reading. （允诺）
He shall be punished. （威胁）
二.Should的用法：
1. Should表示劝告、建议、命令，其同义词是ought to；在疑问句中，通常用should代替ought to。如：
You should go to class right away.
Should I open the window
Should的含义较多，用法较活，现介绍三种其特殊用法。请看下面的句子：
① I should think it would be better to try it again. 我倒是认为最好再试一试。
② You are mistaken, I should say. 依我看，你是搞错了。
③ I should advise you not to do that. 我倒是劝你别这样做。
④ This is something I should have liked to ask you. 这是我本来想问你的。
从以上例句可以看出：情态动词should用于第一人称时可以表示说话人的一种谦逊、客气、委婉的语气。
Should还可以用在if引导的条件从句，表示一件事听起来可能性很小，但也不是完全没有可能。相当于“万一”的意思。从句谓语由should加动词原形构成，主句谓语却不一定用虚拟语气。如：
⑤ Ask her to ring me up if you should see her. 你万一见到她，请让她给我打个电话。
⑥ If you should change your mind, please let us know. 万一你改变主意，请通知我们。
⑦ Should I (If I should) be free tomorrow I will come. 万一我明天有时间，我就来。
此外，Why(or How) + should结构表示说话人对某事不能理解，感到意外、惊异等意思。意为“竟会”。如：
⑧ Why should you be so late today 你几天怎么来得这么晚？
⑨ — Where is Betty living — 贝蒂住在哪里？
— How should I know — 我怎么会知道呢？
⑩ I don't know why you should think that I did it. 我真不知道你凭什么认为这件事是我干的。
2. “should + have + 过去分词”结构一般表示义务，表示应该做到而实际上没有做到，并包含一种埋怨、责备的口气。如： She should have finished it.
I should have helped her, but I never could.
You should have started earlier.
will和would的用法
1. 表示请求、建议等，would比will委婉客气。如：
Would you pass me the book
2. 表示意志、愿望和决心。如：
I will never do that again.
They asked if we would do that again.
The door won't open
3. 用“will be”和“will(would) + have + 过去分词”的结构表示推测，主要用于第二、三人称。前者表示对目前情况的推测，后者表示对已经完成的动作或事态的推测。如：
This will be the book you want.
He will have arrived by now.
The guests would have arrived by that time.
I thought you would have finished this by now.
4. Would可表示过去反复发生的动作或某种倾向。Would表过去习惯时比used to正式，并没有“现已无此习惯”的含义。如：
The wound would not heal.
During the vacation he would visit me every week.
5. 表料想或猜想。如：
It would be about ten when he left home.
What would she be doing there
I thought he would have told you all about it.
ought to的用法
1. Ought to表示应该。如：
You ought to take care of him.
2. 表示推测。注意与must表示推测时的区别：
He must be at home by now. （断定他已到家）
He ought to be home by now. （不十分肯定）
This is where the oil must be. （比较直率）
This is where the oil ought to be. （比较含蓄）
3. “ought to + have + 过去分词”表示过去应做某事而实际未做。如：
You ought to have asked him (but you didn't).
这时，ought to和should可以互相换用。
注意：在美国英语中，ought to用于否定句和疑问句时，to可以省略。如：
Ought you smoke so much
You oughtn't smoke so much.
ought和should的区别：
1.ought语气略强。
2.should较常用。
3.ought在美国英语中用的很少，而should却相当常用。
4.ought属正式用语。
used to，had better，would rather的用法
1. Used to表示过去的习惯动作或状态，现在已不存在，在间接引语 ( http: / / baike. / view / 1929194.htm" \t "_blank )中，其形式可不变。如：
He told us he used to play football when he was young.
在疑问句、否定句、否定疑问句或强调句 ( http: / / baike. / view / 190776.htm" \t "_blank )中，可有两种形式：
疑问句
Did you use to go to the same school as your brother
Used you to go to the same school as your brother
否定句
I usedn't to go there.
I didn't use to go there.
Usedn't 亦可拼作usen't，但发音皆为['ju:snt]。
否定疑问句
Usen't you to be interested in the theatre
Didn't you use to be interested in the theatre
强调句
I certainly used to smoke, but it was a long time ago.
I certainly did use to smoke, but it was a long time ago.
其反意疑问句 ( http: / / baike. / view / 201301.htm" \t "_blank )或简略回答中，也有两种形式：
She used to be very fat, didn't she （口语+常用）/ use(d)n't she （正式+过时）
Did you use to play chess Yes, I did.
Used you to get up early in the morning Yes, I did. (Yes, I used to.)
2. Had better意为“最好”，后接不带to的不定式。如：
— We had better go now.
— Yes, we had (we'd better / we had better).
Hadn't we better stop now (Had we better not stop now )
I think I'd better be going. （用于进行时态，表“最好立即”）
You had better have done that. （用于完成时态，表未完成动作）
注：①had best与had better同意，但较少用。②You had better … 用于同辈或小辈，对长辈不可用。
3. Would rather意为“宁愿”，表选择，后接不带to的不定式。如：
I'd rather not say anything.
Would you rather work on a farm
— Wouldn't you rather stay here
— No, I would not. I'd rather go there.
由于would rather表选择，因而后可接than。如：
I would rather work on a farm than in a factory.
I would rather watch TV than go to see the film.
I would rather lose a dozen cherry trees than that you should tell me one lie.
I'd rather you didn't talk about this to anyone. （句中的'd rather不是情态动词，would在此是表愿望的实义动词）
can (could), may (might)的用法
can (could) 表示说话人能,可以,同意,准许,以及客观条件许可,could 为 can 的过去式。
Can you pass me the books
你能给我递一下书吗
Could you help me, please
请问,你能帮助我吗
What can you do
你能干点什么呢
Can you be sure
你有把握吗
can 和could 只能用于现在式和过去式两种时态,将来时态用 be able to 来表示。
He could help us at all.
他完全可以帮助我们。
With the teacher's help,I shall be able to speak English correctly.
由于老师的帮助,我将能准确地讲英语。
may (might) 可以, 表示说话人同意,许可或请求对方许可。
You may take the book home.
你可以把书带回家去.
May I come in
我可以进来吗
May I use your dictionary
我可以用你的词典吗
You may put on more clothes.
你可以多穿点衣服.
He said he might lend us some money.
他说他可以借给我们一些钱。
may 否定式为 may not, 缩写形式是 mayn't.
might 是may 的过去式, 有两种用法, 一种表示过去式，一种表示虚拟语气, 使语气更加委婉, 客气或对可能性的怀疑。
He told me he might be here on time.
他说他能按时间来。
Might I borrow some money now.
我可以借点钱吗
He might be alive.
他可能还活着。
must, need, ought to, dare (dared)用法
Must 必须,应该,一定,准是, 表示说话人认为有必要做某事, 命令, 要求别人做某事以及对事物的推测。
must 用来指一般现在时 ( http: / / baike. / view / 360594.htm" \t "_blank )和一般将来时, 过去式可用 have to 的过去式代替。
I must finish my work today. 我今天必须完成我的工作。
You mustn't work all the time. 你不能老是工作。
Must I return the book tomorrow 我必须明天还书吗
After such a long walk, you must be tired. 走了这么长的路,你一定困了。
He must be the man I am looking for. 他一定是我要找的人。
He had to go because of somebody's calling him that day. 那天他要走是因为有人叫他。
must + have + 过去分词,表示现在对过去事物的推测。
He must have told my parents about it.
他一定把这件事情告诉我父母亲了。
He must have received my letter now.
他现在一定收到我的信了。
It's six o'clock already, we must have been late again.
已经六点钟了，我们一定又迟到了。
must 和 have to 的区别: must 表示说话人的主观思想, have to 表示客观需要。
You must do it now.
你必需现在就干。(说话人认为必须现在干)
I have to go now.
我得走了。(客观条件必须现在走)
need 需要 多用在否定式或疑问句中.
Need I attend the meeting tomorrow
我需要明天参加会议吗
You need not hand in the paper this week.
这一周你不必交论文。
need 是一个情态动词, 他的用法完全和其他情态动词一样, 但 need 还可当作实义动词使用, 这时 need 就象其他动词一样,有第三人称,单复数, 后面加带 to 的动词等特性。
I need a bike to go to school.
我上学需要一辆自行车。
Do you need a dictionary
你需要词典吗
She needs a necklace.
她需要一条项链。
needn't + have + 过去分词 表示过去做了没必要做的事情。
You needn't have taken it seriously.
这件事情你不必太认真。
dare 敢 多用在否定或疑问句中。
The little girl dare not speak in public.
小女孩不敢在公众面前说话。
Dare you catch the little cat
你敢抓小猫吗
dare 除用作情态动词外,更多的是当实义动词使用, 用法同实义动词一样,要考虑人称,单复数,时态等。
Do you dare to walk in the dark
你敢黑夜走路吗？
He doesn't dare to tell the teacher what happened that day.
他不敢告诉老师那天发生的事。
have to , ought ，will ，Shall , should . ought 应当,应该 后面跟带有 to 的动词不定式 ( http: / / baike. / view / 26732.htm" \t "_blank )。
You ought to read these books if you want to know how to repair the motorcar.
如果你想知道如何修理汽车,你应该读这些书。
You ought to bring the child here.
你应该把孩子带来。
ought + to have done 句型。指过去动作,表示一件事情该做而未做。
You ought to have been here yesterday.
你昨天就应该来。
ought not to have done 句型。表示一件不该做的事情却做了。
You ought not to have taken the book out of the reading-room.
你不应该把书带出阅览室。
will (would)决心,愿望。 would 为 will 的过去式,
可用于各人称。
I'll do my best to catch up with them.
我要尽全力赶上他们。
I'll never do it again, that's the last time.
我再不会做那件事情了,这是最后一次。
He said he would help me.
他说他会帮助我。
will, would用于疑问句表示说话人向对方提出请求或询问,用 would 比 will 更婉转,客气。
It's hot. Will you open the windows
天气太热了,你能打开窗户吗
Will you help me to work it out
你能帮我解这道题吗
Would you like some coffee？
给你来点咖啡怎样？
Shall, should表示命令,警告,允诺,征求,劝告,建议惊奇。
You should hand in the exercise book.
你应该交作业本了。
This should be no problem.
这应该没问题。
Shall we go now.
我们现在可以走了吗
Why should I meet him？
为什么我要见他
have to,不得不,必须,表示客观条件只能如此, 而must 则表示主观思想必须。
I have to go now.
我现在得走了。
I have to cook for my child.
我得给孩子做饭。
You must be here on time next time.
你下次一定要按时来。
We must go to get the timetable ourselves.
我们一定要自己去拿时刻表。
高中英语语法总结大全之情态动词
情态动词的语法特征
1）情态动词不能表示正在发生或已经发生的事情，只表示期待或估计某事的发生。
2）情态动词 除ought 和have 外，后面只能接不带to 的不定式。
3）情态动词没有人称，数的变化，即情态动词第三人称单数不加-s。
4）情态动词没有非谓语形式，即没有不定式，分词，等形式。
情态动词的回答方式
问句 肯定回答 否定回答
Need you… Yes, I must. No,I needn't Must you… /don't have to.
典型例题
1）---Could I borrow your dictionary --Yes, of course, you____.
A. might B. will C. can D. should
答案C.could表示委婉的语气，并不为时态。答语中of course，
表示肯定的语气，允许某人做某事时，用can和 may来表达，不能用 could或might。
复习： will 与you连用，用来提出要求或下命令。 should与you 连用，用来提出劝告。
2）---Shall Itell John about it
---No, you ___. I've told him already. A. needn'tB. wouldn'tC. mustn'tD. shouldn't
答案A。needn't 不必，不用。wouldn't 将不,不会的。mustn't 禁止、不能。 shouldn't不应该。
本题为不需要，不必的意思，应用 needn't。
3）---Don't forget to come to my birthday party tomorrow. ---______.
A. I don't B.I won't C. I can't D. I haven't
答案B.will既可当作情态动词，表请求、建议、也可作为实义动词表"意愿、意志、决心"，本题表示决心，
选B。
带to的情态动词
带to 的情态动词有四个：ought to, have to, used to, be to, 如加上have got to ,(=must), be able to，为六个。
它们的疑问，否定形式应予以注意：
Do they have to pay their bill before the end of the month
She didn't use to play tennis before she was fourteen.
You ought not to have told her all about it. Ought he to see a heart specialist at once.
ought to 本身作为情态动词使用。其他的词作为实义动词使用，变疑问，否定时，须有do 等助动词协助。
典型例题
Tom ought not to ___ me your secret, but he meant no harm.
A.have told B.tell C.be telling D. having told
答案A。由于后句为过去时，告诉秘密的动作又发生在其前因，此地应用过去完成时，但它在情态动词
ought to 后，所以用have。
can 和be able to
1）cancould 表示能力；可能 (过去时用could), 只用于现在式和过去式(could)。be able to可以用于各种时态。
They will be able to tell you the news soon. 他很快就能 告诉你消息了。
2）只用be able to
a. 位于助动词后。b. 情态动词后。 c. 表示过去某时刻动作时。
d. 用于句首表示条件。 e. 表示成功地做了某事时，只能用was/were able to，不能用 could。
He was able to flee Europe before the war broke out. =He managed to flee Europe before the warbroke out.
注意：could不表示时态
1）提出委婉的请求，（注意在回答中不可用could）。
--- Could I have the television on --- Yes, you can. / No,you can't.
2）在否定，疑问句中表示推测或怀疑。
He couldn't be a badman. 他不大可能是坏人。
may和might
1） 表示允许或请求；表示没有把握的推测；may放在句首，表示祝愿。
May God bless you! He might be at home.
注意：might 表示推测时，不表示时态。只是可能性比may 小。
成语： may/might as well，后面接不带to 的不定式，意为"不妨"。
If that is the case, we may as well try.
典型例题
Peter ___come with us tonight, but he isn't very sure yet.
A. must B. may C. can D. will
答案B. 表可能性只能用may.此句意可从后半句推出。
have to和must
1)两词都是'必须'的意思，have to 表示客观的需要，must 表示说话人主观上的看法，既主观上的必要。
My brother was very ill, so I had to call the doctor in the middle of thenight.我弟弟病得很厉害，我只得半夜
里把医生 请来。(客观上需要做这件事)
He said that they must work hard. 他说他们必须努力工作。 （主观上要做这件事）
2)have to有人称、数、时态的变化，而must只有一种形式。但must 可用于间接引语中表示过去的必要或义务。
He had to look after hissister yesterday.
3） 在否定结构中： don't have to表示"不必" mustn't表示"禁止"，
You don't have to tell him about it.你不一定要把此事告诉他。
You mustn't tell him about it.你一定不要把这件事告诉他。
must表示推测
1) must用在肯定句中表示较有把握的推测，意为"一定"。
2) must表对现在的状态或现在正发生的事情的推测时， must 后面通常接系动词be 的原形或行为动词的进行式。
You have worked hard all day.You must be tired.你辛苦干一整天，一定累了。（对现在情况的推测判断）
He must be working in his office. 他一定在办公室工作呢。
比较： He must be staying there. 他现在肯定呆在那里。
He must stay there. 他必须呆在那。
3) must 表示对已发生的事情的推测时，must 要接完成式。
I didn't hear the phone. I must have been asleep.我刚才没有听到电话，我想必是睡着了。
4) must表示对过去某时正发生的事情的推测，must 后面要接不定式的完成进行式。
---Why didn't you answer my phone call ---Well, Imust have been sleeping, so Ididn't hear it.
5) 否定推测用can't。
If Tom didn't leave here until five o'clock, he can't be home yet.如果汤姆五点才离开这儿，他此时一定还未到家。
表示推测的用法 can, could, may, might, must 皆可表示推测，其用法如下：
1）情态动词+动词原形。
表示对现在或将来的情况的推测，此时动词通常为系动词。
I don't know where she is, she may be in Wuhan.
2）情态动词+动词现在进行时。
表示对现在或将来正在进行的情况进行推测。
At this moment, our teacher must be correcting our exam papers. 这时，我们老师想必在批改试卷。
3）情态动词+动词完成时。
表示对过去情况的推测。
We would have finished this work by the end of next December. 明年十二月底前我们很可能已完成这项工作了。
The road is wet. It must have rained last night. 地是湿的，昨天晚上一定下雨了。
4）情态动词+动词的现在完成进行时。 表示对过去正在发生事情的推测。
Your mother must have been looking for you. 你妈妈一定一直在找你。
5）推测的否定形式，疑问形式用can't, couldn't表示。 Mike can't have found his car, for he came to work by bus this morning. 迈克一定还没有找回他的车，因为早上他是坐公共汽车来上班的。
注意：could, might表示推测时不表示时态，其推测的程度不如can, may。
情态动词+have+过去分词
1) may(might) have + done sth, can (could) have + done sth表示过去，推测过去时间里可能发生的事情。
Philip may (might) have been hurt seriously in the car accident.
Philip can (could) have been hurt seriously in the car accident.
2)must have +done sth，对过去时间里可能发生的事情的推测，
语气较强，具有"肯定"，"谅必"的意思。
---Linda hasgone to work, buther bicycle is still here.
---She must have gone by bus.
3) ought to have done sth, should have done sth
本应该做某事，而事实上并没有做。否定句表示"不该做某事而做了"。
You ought to (should) have been more careful in this experiment.
He ought notto have thrownthe old clothes away.（事实上已扔了。）
ought to 在语气上比should 要强。
4) needn't have done sth本没必要做某事 I dressed very warmly for the trip, but Ineedn't have
done so. The weather was hot.
5) would like to have done sth本打算做某事
I would like to have read the article, but I was very busy then.
should和ought to
should 和ought to 都为"应该"的意思，可用于各种人称。
---Ought he to go ---Yes. Ithink he ought to.
表示要求，命令时，语气由 should（应该）、hadbetter最好）、 must（必须）渐强。
had better表示最好
had better 相当于一个助动词，它只有一种形式，它后面要跟动词原形。
Had better do sth had better not do sth
It is pretty cold. You'd better put on my coat.
She'd better not play with the dog. had better have done sth表示与事实相反的结果，意为"本来
最好"。 You had better have come earlier.
Would rather表示"宁愿" would rather do would rather not do
would rather… than…宁愿……而不愿。还有would sooner, hadrather, had sooner都表示"宁愿"、" 宁可"的意思。
If I have a choice, I had sooner not continue my studies at this school.
I would rather stay here than go home. = I would stay here rather than go home.
典型例题
----Shall we go skating or stay at home ----Which ___ do
A. do you rather B. would you rather C. will you rather D. should yourather
答案B。本题考查情态动词rather的用法，would rather +do sth 意为"宁愿"，本题为疑问句，would 提前，所以选B。
will和would would rather do would rather not do would rather… than…宁愿……而不愿。
还有would sooner, hadrather, had sooner都表示"宁愿"、" 宁可"的意思。
If I have a choice, I had sooner not continue my studies at this school.
I would rather stay here than go home. = I would stay here rather than go home.
典型例题
----Shall we go skating or stay at home ----Which ___ do
A. do you rathe rB. would you rather C. will you rather D. should you rather
答案B。本题考查情态动词rather的用法，would rather +do sth 意为"宁愿"，本题为疑问句，would 提前，所以选B。
need和dare
这两词既可做实义动词用，又可做情态动词用。作为情态动词，两者都只能用于疑问句，否定句和条件句。 need 作实义动词时后面 的不定式必须带to，而dare作实义动词用时, 后面的to 时常可以被省略。
1) 实义动词： need（需要,要求） need +n. / to do sth
2) 情态动词： need，只用原形need后加do，否定形式为need not。
Need you go yet Yes, Imust. / No,I needn't.
3) need 的被动含义：need, want, require, worth（形容词） 后面接doing也可以表示被动：
need doing =need to be done
专题：情态动词
（一）情态动词的定义: 情态动词表示说话人对某一动作或状态的态度。
（二）情态动词的特点:
1）有一定词义；2）不受主语人称和数的变化影响；3）与主要动词的原形（或称不带to的不定式）一起构成谓语（除ought to作固定词组看待）。
（三）情态动词的基本用法:
1. can (could)
1）表示能力，could主要指过去时间。
2）表示可能（理论上或是逻辑判断上）。
3）表示允许。
4）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。
5）比较委婉客气地提出问题或陈述看法。
2. may (might)
1）表允许，might可以指过去时间，也可指现在时间，语气更委婉。
在回答以may引起的问句时，多避免用这个词，而用其它方式，如Yes, please. / Certainly.
/ Please don’t ./ You’d better not. / No, you mustn’t.等，以免显得太严峻或不客气。
2）表可能（事实上）。可以指过去时间，也可以指现在时间，但语气更加不肯定。
3. must
1）表示义务。意为“必须”（主观意志）。
2）表示揣测。意为“想必、准是、一定”等，只用于肯定句。
4. shall
1）表征询意见，用于第一、第三人称疑问句。
2）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。
5. will
1）表意愿，用于各种人称陈述句。
2）表请求，用于疑问句。
3）表示某种倾向或习惯性动作。
6. should
1）表义务。意为“应该”（某件事宜于做），用于各种人称。
2）表推测，意为“想必一定、照说应该、估计”等。
7.would
1）表意愿。
2）表委婉地提出请求、建议或看法。
3）表过去反复发生的动作或过去的一种倾向。
8. ought to
1）表义务，意为“应该”（因责任、义务等该做），口气比should稍重。
2）表推测，暗含很大的可能，语气较弱。
9. used to
表示过去的习惯动作或状态，现在不复发生或存在。疑问式和否定式有两种。
（一）need和dare的用法
need和dare既可用作情态动词，也可用作实义动词。用作情态动词时，主要用于否定句和疑问句。用作实义动词时，可用于各种句式。
1.用作情态动词
2.用作实义动词
（二）情态动词后跟完成式和进行式的用法
1. 情态动词后跟完成式，表“应当已经……”，“想必已经……”，“本来可以……”等意。
2. 情态动词后跟进行式，表示“想必正在……”，“可能正在……”，“应当正在”等意。
（三）几组词的辨异
1. can 和be able to
1）情态动词can只有两种时态形式，现在式can和过去式could，而be able to有多种时态形式。
2）用在过去时中，could经常表示能够做某事，事实上不一定去做，而was ∕were able to则表示“过去做成了某事”。在否定句中两者可通用。
2. must和 have to
must表示主观意志，而have to表示由于客观因素不得不做某事。must没有过去式，除在间接引语中可用于表示过去时间，在直接引语中表示过去时间应该用had to代替。
3. would和used to
1）used to表示过去与现在或过去某时与后来的情况有不同，而would只表过去的情况。
2）used to可表示过去的习惯动作和经常的情况，而would只表示过去的习惯动作。
情态动词的用法：
常用的情态动词有can，may，must，need,should, had better.
1. can 的用法：
① 表示能力 “能，会” eg: He can speak a little Japanese.他会说一点日语。
② 表示请求或许可 “可以” eg: Can I help you 要我帮忙吗
③ 表示猜测 “可能” eg: Where can she go now 她可能到哪里去了呢
2.may 的用法：
①表示请求或允许 “可以”“准许” eg: May I go home，please 请问我可以回家吗
② 表示可能性 “ 可能”、也许” eg: I think it may rain this afternoon. 我想今天下午可能下雨。
注：might为may的过去式，但也可以代替may，语气较为婉转客气或更加不肯定。
eg: ① He might not come today.今天他也许不来了。(语气不肯定)
②You might also get a headache when you work too hard，当你工作太努力时，你也可能患头痛
3. must的用法：
①表示义务、必要或命令 “必须、应该” eg: You must come early tomorrow．你明天得早来。
② 表示推测时“肯定，一定” eg: They must be at home.The light is on 他们肯定在家,灯亮着呢.
③ must not 禁止，不许 eg: You must not tell lies. 你不许撒谎。
注意： ①must开头的疑问句，其否定回答通常用 don't have to 或needn't 。而不用mustn't
eg: ---Must I finish my homework first 我必须先完成作业吗？
---No, you don't have to/ needn't. 不，你不必。
② can 和 must在 表推测时，can一般否定句中，而must 常用于肯定句中。
eg: ①It can not be Li Lei 那个人不可能是李磊
② It must be Li Lei 那个人肯定是李磊。
4. need 的用法：
① 情态动词 “需要, 有必要”一般用于否定句或疑问句中。
eg: You needn't come here this afternoon.你今天下午不必来。
② 行为动词 “需要, 有必要” 可以用于各种句式中。
eg: ①You don't need to go now. 你不必现在就走。
② I need to have a rest. 我需要休息一下
③ Do we need to finish all the work today 我们今天需要完成所有的工作吗？
need的用法的助记口诀：
实义动词表“需要”，后接名、代、不定式。 need后接动名词，主动形式表被动。
情态动词表“需要”，没有人称 数之变。 其后直接加动原，多用疑问与否定。
5.征求许可或给予许可，“我可以···？”用句型“Can/May/Could/Might I... ”其中"Can I... "属于非正式用法，
"May I ... "属于正式用法。"Could/Might I... "的回答通常不用could或might，而用may或can或其他表示客
气的词语。
6.肯定句中表推测“可能”：can,could,may,might都可以在肯定句中表“可能”。其中can的语气最强，可能性
最大，其余依次递减。 肯定句中表推测“一定，肯定”用must.
7.疑问句中表推测“可能”：用can,could,might,而不能用may. mustn't 不表示推测，而表示禁止。
意义为“禁止，不准”
8.否定句中表推测： may not/might not：可能不 can not/could not： 不可能
eg: ①You may not be right．你也许不对. ② You can not be right．你不可能对.
9.以may（表许可或请求）开头的一般疑问句的肯定回答用may，否定回答用mustn't或can't。
10.表示“必须”时，must表示主观看法，have to强调客观需要。
11.ought to和should两者都表示应该，但是ought to比should语气强。
12.would rather与than连用，其结构是：would rather...than...或would...rather than...。would(rather)和than后面
都接动词原形，如果用的动词相同，则than后省去该动词。would rather...than...的意义为“宁愿···而不是···”
eg:I would rather play football than baseball.我宁愿踢足球而不愿打棒球。
13. 情态动词的助记口诀：
情态动词两要点：动词原形跟后边 没有人称 、数之变
can 表能力 may许可 must来把责任担（必须） 否定回答need换。
need需要 dare敢 should应该 would like 愿(意) have to“ 不得不”表客观。
14.had better用法的助记口诀：
表示“建议”和“忠告”，had better 为最好。 建议某人“最好不···”，要用 had better not do。
情态动词的用法要点
can和could
情态动词 用法 例句
can/could 表示能力 1．“I don’t think Mike can type.” “Yes, he can.”2．I can speak fluent English now , but I couldn’t 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。要表达具体某事实际发生的可能性时，不用can，需用could，may，might。 As a human being, anyone can make a mistake.I’m confident that a solution can be found.He can be very forgetful sometimes.I may stay at home this weekend.（实际可能性）Peter might come to join us.(实际可能性) 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。 Can we turn the air conditioner on Any police officer can insist on seeing a driver’s license.In soccer, you can’t touch the ball with your hands.Could you have her call me back when she gets home, please 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。 It can’t be easy caring for a man and a child who are not your own.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。 Can this be an excuse for not giving them help This can’t be true.How can you be so crazy.
特别说明：
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, I’m afraid not.)
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：
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 用法 例句
may/might 表示允许、许可。否定回答一般用must not/mustn’t,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。 May I come in and wait ——May I smoke here ——No, you mustn’t(或No, you’d 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。 Might I borrow your pen 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。 It may rain this afternoon.She might come to join us this afternoon.I suppose he might have missed the train.
may用于祈使句表示祝愿 May you succeed.Long may he live! 愿他能持续住下去。May you have many more days as happy as this one.May she rest in peace.愿她安息。
惯用句式：“may well+ 动词原形”，意为“完全能，很可能”，相当于to be very likely to“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. It may well change forever the way you look at Greek art.There may well be a real problem here.There is nothing to do, so I may as well go to bed.You may as well tell us now, we’ll find out sooner or later.I suppose we might as well go home.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mustn’t表示“不准，不应该，禁止”等意 You must come to school on time.Everybody must obey the law.You mustn’t drive so fast in the street.We mustn’t waste any more time.
在回答带有must的问句时，否定回答常用needn’t或don’t have to，表示“不必”，而不用mustn’t 1．—Must I come back before ten —Yes，you must.(No, you needn’t)
表示有把握的推测，意为“一定、准是、相必”，只用于肯定句中 It must be my mother.You must be hungry after a walk.There must be a hole in the wall.
have tohave 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。 The film is not interesting. I really must go now.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。 1．I had to work hard when I was your age.2．I will have to learn how to use a computer.3．In order to take the exam, we’ll have to finish the whole book by the end of this month .
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。 You mustn’t go there.You don’t have to go there.
补：
情态动词can、may、must的横向辨析
一、表示“能力”。
l．只可用can（could）。may、must则无此种含义。
例：①I can swim now，but I couldn’t last year.
②Can you play me piano？Yes，I can．
2．can（could）适用于各种句型和人称。
例：①肯定句：I（You，He）can swim.
②否定句：I（You，He）can’t swim.
③疑问句：Can I（you，he）swim？
二、表示“请求”或“许可”。can、may、must都可用，但语气和程度不同。
1．can（could）用于各种句型和大部分人称。
例：①肯定句：You（He，We）can go now．
②否定句：You（He，We）can’t go now．
③疑问句：Can I（you，he）go now？
Yes，you can．（No，you can’t．）
2．may（might）用于各种句型，但在肯定句和否定句中不用于第一人称；在疑问句中不用于第二人称。
例：①肯定句：You（He）may go now．
②否定句：You（He）may not go now．
③疑问句：May I（he）go now？
正规回答：（表定）Yes，you may．
（否定）No，you may not．（No，you can’t．／No，you mustn’t．）
口语化回答：（肯定）Yes，please．（Certainly．）
（否定）No，please don’t．（No，of course not．）
3．must用于各种句型和大部分人称。
例：①肯定句：I（You，He）must go now．
②否定句：You（He）mustn’t go now．
③疑问句：Must（you，he）go now？
肯定回答：Yes，you must.
否定回答：No，you needn’t．（No，you don’t have to．）
4．试比较：
You may not smoke here．（不可以）语气轻
You can’t smoke here．（不能）重
You mustn’t smoke here．（决不可）最重
三、表示“可能”、“或许”和“推测”之意。can、may、must都可用，但语气和程度不同。
l．can （could）常用于否定句和疑问句中，could表示的“可能性”更小。
例：①否定句：It couldn’t be him，for he’s at the library．
②疑问句：Can he have gone out？
What can they be doing now？
2．may（might）用于肯定句和否定句中，might表示的“可能性”更小。
例：①肯定句：He may be right．
②否定句：She might not have come yet．
3．must用于肯定句中。
例：①You must be very hungry．（对现在情况猜测）
②Aqiao must have met a fairy．（对过去事实的猜测）
③Everything is clean and tidy．Someone must have cleaned my room．（同上）
4．试比较：
He might not have gone out．（或许没有）
He can’t have gone out．（不可能）
He must have been in the room．（一定、准是）
以上三句可能性逐渐加大至肯定。
练习题：
一、说明下列句中情态动词的含义。（A．能力；B．许可；C．猜测）。
（ ） l. “You must write more neatly,” said the teacher．
（ ） 2. He’s not in the office．He must have gone to the meeting．
（ ） 3. Visitors mustn’t move and touch the exhibits．
（ ） 4. The girl can play the violin very well．
（ ） 5. Can I smoke here？
二、用can（could），may（might），must填充。
1. When I was young，I_____ run very fast．
2. What _____ I do for you，Li Hat？
3. I wonder where Ann is．She _________ be with Dick，I think．
4. A：That pen _______ be his．
B：No，it _______（not）be his．
5. Could I use your phone？Yes，of course you _________.
四．shall和should
情态动词 用法 例句
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 Shall I open the window Shall we say 6 o’clock, then What shall I get for dinner
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。 Don’t worry, you shall get the answer this afternoon.(允诺)He shall be sorry for it one day, I tell you. （警告）You shall do as I say. (命令)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” What should I do Should I trust him 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” It should be a nice day tomorrow.Try phoning Robert, he should be home now.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 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)Should I be free tomorrow, I’ll come. (万一我明天有时间，我就过来)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，表示意外、惊异的情绪，意为“竟会”，与why，what，how，who连用，如果是疑问句，则不需要回答。 Why should anyone want to marry Tony Don’t ask me. How should I know
五．will和would
情态动词 用法 例句
will/would 用于表示意志或意愿。will指现在，would指过去。 He is the man who will go his own way. (他首歌自行其是的人。)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。 Will you please take a message for him 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。 Fish will die without water.People will talk. (人们总会说闲话。)When we worked in the same office, we would often have coffee together.
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。 These things will happen.That will be the messenger ringing.It would be about ten o’clock when he left home.
表示功能，意为“能，行”。惯用形式：will do/would do表示“解决问题”、“就行”。 That will be all right.Either pen will do.It would not do to work too late.（工作太晚不行。）
用于否定句中，意为“不肯”、“不乐意” 1．I won’t listen to your nonsense.2．No matter what I said, he wouldn’t listen to me.
特别说明：would与used to辨析
would可用来表示过去反复出现的动作，但不能表示过去存在的状态，所以我们不能说：“she would be a quiet girl.”
另外，would强调过去某种特定情况下的活动，是完全过去的事情，同现在没有联系。而used to则着眼于过去和现在的对比，隐含现在已不存在，动作或状态都可表示。Would可以表示不规则的习惯，used to则不可。如：
He used to be a naughty boy and cause trouble.
I used to get up at six in the morning.
Sometimes she would take a walk in the neighboring woods.
In those days, whenever I had difficulties, I would go to Mr. Chen for help.
六．need和dare
情态动词 用法 例句
need 用于表示“需要，必要”之意。做情态动词时，仅用于否定句和疑问句，只有现在时，过去式要用needn't have，疑问式用need+人称 ,否定式用need not(即needn't）， 1．—Need we leave soon —Yes, you must.(No, you needn't)2．You needn't have hurried.(=It was not necessary for you to hurry，but you did).你当时不必这么匆忙。
做实义动词时，其变化与一般的实义动词相同，后接带to的不定式（need doing = need to be done ）,过去式用needed、did you need 和didn't need,肯定式用needs/needed/need,疑问式用do、does、did提问，否定式要在前面加don't、doesn't、didn't 1. A job like nursing needs patience and understanding.(need+名词，need understanding=need to be understood,需要被理解)2．He needs to see a doctor.(need to do)3．Do you still need volunteers to help clean up after the party (need somebody to do something) 4．They didn't need to start so early.(do not need to do)
dare 用于表示“敢于”之意。做情态动词，没有人称和数的变化，主要用于否定句、疑问句和条件状语从句中 1．—Dare you tell her the truth —Yes, I dare. /No, I daren’t.How dare you accuse me of lying!He daren’t admit this.
用作实义动词时，其变化与一般的实义动词相同。在肯定句中，dare后接带to的不定式；否定句中，dare后既可接带to的不定式，也可接不带to的不定式。 Only a few journalists dared to cover the story.He doesn’t dare (to) go there alone.Don’t you dare (to) touch it
七．ought的用法：
情态动词 用法 例句
ought to do 表示“应该”之意 You ought to take care of him.—Ought I go now —Yes, you ought to. /No, you oughtn’t to.
表示推测。注意与must表示推测是的区别 He must be home by now. (断定他已到家)He ought to be home by now. (不十分肯定)This is where the oil must be. (比较直率)This is where the oil ought to be. (比较含蓄)
说明：should与ought to 表示“应该”时的区别
should 表示自己的主观看法，而ought to的语气中，含有“按道理应该……”之意。若要反映客观情况或涉及法律义务和规定，一般用ought to。如：
You should help them with their work.
You are his father. You ought to get him to receive good education.
八．“情态动词+have done”用法
情态动词+have done 用法 例句
must have done 表示主观上对过去已经发生的行为进行推测，意为“想必，准是，一定做了某事” She must have gone through a lot.He must have visited the White House during his stay in the United States.
may/might have done 表示对过去已发生行为的推测，意为“也许/或许已经（没有）……“。一般用于肯定句或否定句中，不用于疑问句。用might则表示语气更加不肯定。 You may have learnt the news.He may not have heard his name called.Sorry I’m late. I might have turned off the alarm clock and gone back to sleep again.
can…have donecannot have done 表示对过去发生的行为的怀疑和不肯定，通常用在否定句和疑问句中。（can换成could时语气委婉） Where can she have gone Could he have done such a foolish thing The boy can’t have finished reading the book so soon because it is difficult even to an adult.
could have done 可用于肯定句中，表示“可能已经……”之意，此外，还可以表示过去能做而没做的事，有一种对过去为付诸实施的事情的惋惜。 He could have killed himself driving at a dangerous speed.You could have been more considerate.You could have done better, but you were too careless.
might have done 表示“本来可能……，但实际上没有发生的事情”。另外，还可以表示“本来应该或可以做某事”之意，含有轻微的责备语气。 You should not swum in that sea. You might have been eaten by a shark.He might have given him more help, thought he was busy.
should/ought to have done 用于肯定句时，表示本该做某事，而实际上未做；用于否定句时，则表示不该做的事反而做了。 He should have known that the police would never allow this sort of thing.You shouldn’t have done it so carelessly.You ought to have returned the book earlier.You ought not to have refused his offer.
needn’t have done 表示做了本来不必去做的事。注意：didn’t need to do表示“没必要做而实际上也没有做某事” You needn’t have watered the plants, for it is going to rain.I didn’t need to buy the dictionary. I had a copy at home.
had better have done 用于事后的建议，含轻微责备的口吻，意为“当时最好做了某事”，其否定式had better not have done表示相反的含义。 You had better have started earlier.You had better not have scolded her.
would rather have done 表示“当时宁愿做了某事”，其否定式would rather not have done表示相反的含义，两者都表示“后悔”之意。 1．I would rather have taken his advice.2．I would rather not have told him the truth.
补：
can和could的用法
1. 表示能力或客观可能性，还可以表示请求和允许。如：
Can you finish this work tonight
你今晚能完成这项工作吗？
Man can not live without air.
人离了空气不能活。
— Can I go now — Yes, you can.
—我现在可以走了吗？—你可以。
注意：①could也可表示请求，语气委婉，主要用于疑问句，不可用于肯定句，答语应用can（即could不能用于现在时态的简略答语中）。如：
Could I come to see you tomorrow
我明天能来看您吗？
Yes, you can. （否定答语可用No, I'm afraid not.）
是的，你可以。（不，恐怕不行。）
②can表示能力时，还可用be able to代替。如：
I'll not be able to come this afternoon.
我今下午不能来。
2. 表示惊异、怀疑、不相信的态度。（主要用在否定句、疑问句或惊叹句中）
Can this be true
这可能是真的吗？
How can you be so careless!
你怎么能这么粗心！
This can not be done by him.
这不可能是他做的。
3. “can(could) + have + 过去分词”的疑问或否定形式表示对过去发生的行为怀疑或不肯定。如：
He can not have been to that town.
他不可能去过那个镇。
Can he have got the book
他可能拥有这本书吗？
4. 用在疑问句及否定句中,表示惊讶,不相信等.
5. can not```too\enough表示"无论怎样``````也不过分","越``````越好"
6.can 可以表示体力活脑力方面的能力，能够，能，会
Can you finish the work in such a short time
你能在那么短的时间内完成这项工作吗？
7. can 表示许可、允许 ， 在疑问句中表示要求，在否定句中表示不许，此时可以和may通用。
may和might的用法
1. 表示许可。
表示请求、允许时，might比may的语气更委婉一些，否定回答时(口语中常用) no , you can't . or , yes, please 用mustn't表示“不可以”、“禁止”、“阻止”之意(具有强烈禁止的意思)如：
You may drive the car.
你可以开这辆车。
— Might I use your pen — No, you mustn't.
—我可以用你的钢笔吗？—不，绝对不行。
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。在日常口语中，用Can I ... 征询对方意见在现代口语中更为常见。
2. 用于祈使句 ( http: / / baike. / view / 46257.htm" \t "_blank )中表示祝愿。如：
May you succeed!
祝你成功！
3. 表示推测、可能（疑问句不能用于此意）。
He may be very busy now.
他现在可能非常忙。
4. “may(might) + have + 过去分词”表示对过去发生的行为的推测。如：
He may not have finished the work.
他可能没有完成工作。
must和have to的用法
1. 表示必须、必要。（must表示主观多一些而have to则表示客观多一些）如：
You must come in time.
你必须及时过来。
回答must引出的问句时，如果是否定的回答，不能用mustn't，而要用needn't或don't have to。
— Must we hand in our exercise books today
— Yes, you must. (No, you don’t have to.)
—我们今天必须交上练习册吗？
—是的。（不，不必。）
2. “must be + 表语”的结构表示推测，它的否定或疑问式用can代替must。
This must be your pen.
这一定是你的钢笔。
3. “must + have + 过去分词”的结构常用在肯定句中，表示对过去发生的行为的推测。它的否定或疑问式用can代替must。
He must have been to Shanghai.
他一定去过上海。
4. have to的含义与must相似，两者往往可以互换使用，但have to有各种形式，随have的变化而定。must与have to有下列几点不同：
① 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。如：
The play is not interesting. I really must go now.
这部剧没意思。我真的必须现在就走。
I had to work when I was your age.
当我像你这么大时，我不得不工作。
② must一般只表现在，have则有更多的时态形式。
③ 二者的否定意义不大相同。如：
You mustn't go. 你可不要去。
You don't have to go. 你不必去。
④ 询问对方的意愿时应用must。如：
Must I clean all the room
我一定要打扫整个房间吗？
注意：have to也可拼做have got to。
5. 表示一种与说话人 愿望相反、不耐烦的感彩，偏偏、非要。
Why must you always bother me
为什么你总是来烦我？
dare和need的用法
1. need表示“需要”或“必须”，作情态动词时，仅用于否定句或疑问句中，在肯定句中一般用must, have to, ought to,或should代替。如：
You needn’t come so early.
— Need I finish the work today
— Yes, you must.
注意：needn't + 不定式的完成式“表示本来不必做某事而实际上做了某事”。如：
You needn't have waited for me.
2. Dare作情态动词时，主要用于疑问句、否定句和条件从句 ( http: / / baike. / view / 2066094.htm" \t "_blank )中，一般不用在肯定句中。如：
How dare you say I'm unfair.
He daren't speak English before such a crowd, dare he
3. Dare和need常用作实义动词，有时态、人称和数的变化，所不同的是，作实义动词时，在肯定句中，dare后面通常接带to的不定式，在否定和疑问句中，dare后面可接带to或不带to的不定式。如：
I dare to swim across this river.
He does not dare (to) answer.
Don't you dare (to) touch it!
I wondered he dare (to) say that.
He needs to finish it this evening.
shall和should的用法
一.Shall的用法：
1. Shall用于第一人称，表示征求对方的意愿。如：
What shall we do this evening
2. Shall用于第一、第三人称疑问句中，表示说话人征求对方的意见或向对方请示。如：
Shall we begin our lesson
When shall he be able to leave the hospital
3. Shall用于第二、第三人称，表示说话人给对方命令、警告、允诺或威胁。如：
You shall fail if you don't work harder. （警告）
He shall have the book when I finish reading. （允诺）
He shall be punished. （威胁）
二.Should的用法：
1. Should表示劝告、建议、命令，其同义词是ought to；在疑问句中，通常用should代替ought to。如：
You should go to class right away.
Should I open the window
Should的含义较多，用法较活，现介绍三种其特殊用法。请看下面的句子：
① I should think it would be better to try it again. 我倒是认为最好再试一试。
② You are mistaken, I should say. 依我看，你是搞错了。
③ I should advise you not to do that. 我倒是劝你别这样做。
④ This is something I should have liked to ask you. 这是我本来想问你的。
从以上例句可以看出：情态动词should用于第一人称时可以表示说话人的一种谦逊、客气、委婉的语气。
Should还可以用在if引导的条件从句，表示一件事听起来可能性很小，但也不是完全没有可能。相当于“万一”的意思。从句谓语由should加动词原形构成，主句谓语却不一定用虚拟语气。如：
⑤ Ask her to ring me up if you should see her. 你万一见到她，请让她给我打个电话。
⑥ If you should change your mind, please let us know. 万一你改变主意，请通知我们。
⑦ Should I (If I should) be free tomorrow I will come. 万一我明天有时间，我就来。
此外，Why(or How) + should结构表示说话人对某事不能理解，感到意外、惊异等意思。意为“竟会”。如：
⑧ Why should you be so late today 你几天怎么来得这么晚？
⑨ — Where is Betty living — 贝蒂住在哪里？
— How should I know — 我怎么会知道呢？
⑩ I don't know why you should think that I did it. 我真不知道你凭什么认为这件事是我干的。
2. “should + have + 过去分词”结构一般表示义务，表示应该做到而实际上没有做到，并包含一种埋怨、责备的口气。如： She should have finished it.
I should have helped her, but I never could.
You should have started earlier.
will和would的用法
1. 表示请求、建议等，would比will委婉客气。如：
Would you pass me the book
2. 表示意志、愿望和决心。如：
I will never do that again.
They asked if we would do that again.
The door won't open
3. 用“will be”和“will(would) + have + 过去分词”的结构表示推测，主要用于第二、三人称。前者表示对目前情况的推测，后者表示对已经完成的动作或事态的推测。如：
This will be the book you want.
He will have arrived by now.
The guests would have arrived by that time.
I thought you would have finished this by now.
4. Would可表示过去反复发生的动作或某种倾向。Would表过去习惯时比used to正式，并没有“现已无此习惯”的含义。如：
The wound would not heal.
During the vacation he would visit me every week.
5. 表料想或猜想。如：
It would be about ten when he left home.
What would she be doing there
I thought he would have told you all about it.
ought to的用法
1. Ought to表示应该。如：
You ought to take care of him.
2. 表示推测。注意与must表示推测时的区别：
He must be at home by now. （断定他已到家）
He ought to be home by now. （不十分肯定）
This is where the oil must be. （比较直率）
This is where the oil ought to be. （比较含蓄）
3. “ought to + have + 过去分词”表示过去应做某事而实际未做。如：
You ought to have asked him (but you didn't).
这时，ought to和should可以互相换用。
注意：在美国英语中，ought to用于否定句和疑问句时，to可以省略。如：
Ought you smoke so much
You oughtn't smoke so much.
ought和should的区别：
1.ought语气略强。
2.should较常用。
3.ought在美国英语中用的很少，而should却相当常用。
4.ought属正式用语。
used to，had better，would rather的用法
1. Used to表示过去的习惯动作或状态，现在已不存在，在间接引语 ( http: / / baike. / view / 1929194.htm" \t "_blank )中，其形式可不变。如：
He told us he used to play football when he was young.
在疑问句、否定句、否定疑问句或强调句 ( http: / / baike. / view / 190776.htm" \t "_blank )中，可有两种形式：
疑问句
Did you use to go to the same school as your brother
Used you to go to the same school as your brother
否定句
I usedn't to go there.
I didn't use to go there.
Usedn't 亦可拼作usen't，但发音皆为['ju:snt]。
否定疑问句
Usen't you to be interested in the theatre
Didn't you use to be interested in the theatre
强调句
I certainly used to smoke, but it was a long time ago.
I certainly did use to smoke, but it was a long time ago.
其反意疑问句 ( http: / / baike. / view / 201301.htm" \t "_blank )或简略回答中，也有两种形式：
She used to be very fat, didn't she （口语+常用）/ use(d)n't she （正式+过时）
Did you use to play chess Yes, I did.
Used you to get up early in the morning Yes, I did. (Yes, I used to.)
2. Had better意为“最好”，后接不带to的不定式。如：
— We had better go now.
— Yes, we had (we'd better / we had better).
Hadn't we better stop now (Had we better not stop now )
I think I'd better be going. （用于进行时态，表“最好立即”）
You had better have done that. （用于完成时态，表未完成动作）
注：①had best与had better同意，但较少用。②You had better … 用于同辈或小辈，对长辈不可用。
3. Would rather意为“宁愿”，表选择，后接不带to的不定式。如：
I'd rather not say anything.
Would you rather work on a farm
— Wouldn't you rather stay here
— No, I would not. I'd rather go there.
由于would rather表选择，因而后可接than。如：
I would rather work on a farm than in a factory.
I would rather watch TV than go to see the film.
I would rather lose a dozen cherry trees than that you should tell me one lie.
I'd rather you didn't talk about this to anyone. （句中的'd rather不是情态动词，would在此是表愿望的实义动词）
can (could), may (might)的用法
can (could) 表示说话人能,可以,同意,准许,以及客观条件许可,could 为 can 的过去式。
Can you pass me the books
你能给我递一下书吗
Could you help me, please
请问,你能帮助我吗
What can you do
你能干点什么呢
Can you be sure
你有把握吗
can 和could 只能用于现在式和过去式两种时态,将来时态用 be able to 来表示。
He could help us at all.
他完全可以帮助我们。
With the teacher's help,I shall be able to speak English correctly.
由于老师的帮助,我将能准确地讲英语。
may (might) 可以, 表示说话人同意,许可或请求对方许可。
You may take the book home.
你可以把书带回家去.
May I come in
我可以进来吗
May I use your dictionary
我可以用你的词典吗
You may put on more clothes.
你可以多穿点衣服.
He said he might lend us some money.
他说他可以借给我们一些钱。
may 否定式为 may not, 缩写形式是 mayn't.
might 是may 的过去式, 有两种用法, 一种表示过去式，一种表示虚拟语气, 使语气更加委婉, 客气或对可能性的怀疑。
He told me he might be here on time.
他说他能按时间来。
Might I borrow some money now.
我可以借点钱吗
He might be alive.
他可能还活着。
must, need, ought to, dare (dared)用法
Must 必须,应该,一定,准是, 表示说话人认为有必要做某事, 命令, 要求别人做某事以及对事物的推测。
must 用来指一般现在时 ( http: / / baike. / view / 360594.htm" \t "_blank )和一般将来时, 过去式可用 have to 的过去式代替。
I must finish my work today. 我今天必须完成我的工作。
You mustn't work all the time. 你不能老是工作。
Must I return the book tomorrow 我必须明天还书吗
After such a long walk, you must be tired. 走了这么长的路,你一定困了。
He must be the man I am looking for. 他一定是我要找的人。
He had to go because of somebody's calling him that day. 那天他要走是因为有人叫他。
must + have + 过去分词,表示现在对过去事物的推测。
He must have told my parents about it.
他一定把这件事情告诉我父母亲了。
He must have received my letter now.
他现在一定收到我的信了。
It's six o'clock already, we must have been late again.
已经六点钟了，我们一定又迟到了。
must 和 have to 的区别: must 表示说话人的主观思想, have to 表示客观需要。
You must do it now.
你必需现在就干。(说话人认为必须现在干)
I have to go now.
我得走了。(客观条件必须现在走)
need 需要 多用在否定式或疑问句中.
Need I attend the meeting tomorrow
我需要明天参加会议吗
You need not hand in the paper this week.
这一周你不必交论文。
need 是一个情态动词, 他的用法完全和其他情态动词一样, 但 need 还可当作实义动词使用, 这时 need 就象其他动词一样,有第三人称,单复数, 后面加带 to 的动词等特性。
I need a bike to go to school.
我上学需要一辆自行车。
Do you need a dictionary
你需要词典吗
She needs a necklace.
她需要一条项链。
needn't + have + 过去分词 表示过去做了没必要做的事情。
You needn't have taken it seriously.
这件事情你不必太认真。
dare 敢 多用在否定或疑问句中。
The little girl dare not speak in public.
小女孩不敢在公众面前说话。
Dare you catch the little cat
你敢抓小猫吗
dare 除用作情态动词外,更多的是当实义动词使用, 用法同实义动词一样,要考虑人称,单复数,时态等。
Do you dare to walk in the dark
你敢黑夜走路吗？
He doesn't dare to tell the teacher what happened that day.
他不敢告诉老师那天发生的事。
have to , ought ，will ，Shall , should . ought 应当,应该 后面跟带有 to 的动词不定式 ( http: / / baike. / view / 26732.htm" \t "_blank )。
You ought to read these books if you want to know how to repair the motorcar.
如果你想知道如何修理汽车,你应该读这些书。
You ought to bring the child here.
你应该把孩子带来。
ought + to have done 句型。指过去动作,表示一件事情该做而未做。
You ought to have been here yesterday.
你昨天就应该来。
ought not to have done 句型。表示一件不该做的事情却做了。
You ought not to have taken the book out of the reading-room.
你不应该把书带出阅览室。
will (would)决心,愿望。 would 为 will 的过去式,
可用于各人称。
I'll do my best to catch up with them.
我要尽全力赶上他们。
I'll never do it again, that's the last time.
我再不会做那件事情了,这是最后一次。
He said he would help me.
他说他会帮助我。
will, would用于疑问句表示说话人向对方提出请求或询问,用 would 比 will 更婉转,客气。
It's hot. Will you open the windows
天气太热了,你能打开窗户吗
Will you help me to work it out
你能帮我解这道题吗
Would you like some coffee？
给你来点咖啡怎样？
Shall, should表示命令,警告,允诺,征求,劝告,建议惊奇。
You should hand in the exercise book.
你应该交作业本了。
This should be no problem.
这应该没问题。
Shall we go now.
我们现在可以走了吗
Why should I meet him？
为什么我要见他
have to,不得不,必须,表示客观条件只能如此, 而must 则表示主观思想必须。
I have to go now.
我现在得走了。
I have to cook for my child.
我得给孩子做饭。
You must be here on time next time.
你下次一定要按时来。
We must go to get the timetable ourselves.
我们一定要自己去拿时刻表。
高中英语语法总结大全之情态动词
情态动词的语法特征
1）情态动词不能表示正在发生或已经发生的事情，只表示期待或估计某事的发生。
2）情态动词 除ought 和have 外，后面只能接不带to 的不定式。
3）情态动词没有人称，数的变化，即情态动词第三人称单数不加-s。
4）情态动词没有非谓语形式，即没有不定式，分词，等形式。
情态动词的回答方式
问句 肯定回答 否定回答
Need you… Yes, I must. No,I needn't Must you… /don't have to.
典型例题
1）---Could I borrow your dictionary --Yes, of course, you____.
A. might B. will C. can D. should
答案C.could表示委婉的语气，并不为时态。答语中of course，
表示肯定的语气，允许某人做某事时，用can和 may来表达，不能用 could或might。
复习： will 与you连用，用来提出要求或下命令。 should与you 连用，用来提出劝告。
2）---Shall Itell John about it
---No, you ___. I've told him already. A. needn'tB. wouldn'tC. mustn'tD. shouldn't
答案A。needn't 不必，不用。wouldn't 将不,不会的。mustn't 禁止、不能。 shouldn't不应该。
本题为不需要，不必的意思，应用 needn't。
3）---Don't forget to come to my birthday party tomorrow. ---______.
A. I don't B.I won't C. I can't D. I haven't
答案B.will既可当作情态动词，表请求、建议、也可作为实义动词表"意愿、意志、决心"，本题表示决心，
选B。
带to的情态动词
带to 的情态动词有四个：ought to, have to, used to, be to, 如加上have got to ,(=must), be able to，为六个。
它们的疑问，否定形式应予以注意：
Do they have to pay their bill before the end of the month
She didn't use to play tennis before she was fourteen.
You ought not to have told her all about it. Ought he to see a heart specialist at once.
ought to 本身作为情态动词使用。其他的词作为实义动词使用，变疑问，否定时，须有do 等助动词协助。
典型例题
Tom ought not to ___ me your secret, but he meant no harm.
A.have told B.tell C.be telling D. having told
答案A。由于后句为过去时，告诉秘密的动作又发生在其前因，此地应用过去完成时，但它在情态动词
ought to 后，所以用have。
can 和be able to
1）cancould 表示能力；可能 (过去时用could), 只用于现在式和过去式(could)。be able to可以用于各种时态。
They will be able to tell you the news soon. 他很快就能 告诉你消息了。
2）只用be able to
a. 位于助动词后。b. 情态动词后。 c. 表示过去某时刻动作时。
d. 用于句首表示条件。 e. 表示成功地做了某事时，只能用was/were able to，不能用 could。
He was able to flee Europe before the war broke out. =He managed to flee Europe before the warbroke out.
注意：could不表示时态
1）提出委婉的请求，（注意在回答中不可用could）。
--- Could I have the television on --- Yes, you can. / No,you can't.
2）在否定，疑问句中表示推测或怀疑。
He couldn't be a badman. 他不大可能是坏人。
may和might
1） 表示允许或请求；表示没有把握的推测；may放在句首，表示祝愿。
May God bless you! He might be at home.
注意：might 表示推测时，不表示时态。只是可能性比may 小。
成语： may/might as well，后面接不带to 的不定式，意为"不妨"。
If that is the case, we may as well try.
典型例题
Peter ___come with us tonight, but he isn't very sure yet.
A. must B. may C. can D. will
答案B. 表可能性只能用may.此句意可从后半句推出。
have to和must
1)两词都是'必须'的意思，have to 表示客观的需要，must 表示说话人主观上的看法，既主观上的必要。
My brother was very ill, so I had to call the doctor in the middle of thenight.我弟弟病得很厉害，我只得半夜
里把医生 请来。(客观上需要做这件事)
He said that they must work hard. 他说他们必须努力工作。 （主观上要做这件事）
2)have to有人称、数、时态的变化，而must只有一种形式。但must 可用于间接引语中表示过去的必要或义务。
He had to look after hissister yesterday.
3） 在否定结构中： don't have to表示"不必" mustn't表示"禁止"，
You don't have to tell him about it.你不一定要把此事告诉他。
You mustn't tell him about it.你一定不要把这件事告诉他。
must表示推测
1) must用在肯定句中表示较有把握的推测，意为"一定"。
2) must表对现在的状态或现在正发生的事情的推测时， must 后面通常接系动词be 的原形或行为动词的进行式。
You have worked hard all day.You must be tired.你辛苦干一整天，一定累了。（对现在情况的推测判断）
He must be working in his office. 他一定在办公室工作呢。
比较： He must be staying there. 他现在肯定呆在那里。
He must stay there. 他必须呆在那。
3) must 表示对已发生的事情的推测时，must 要接完成式。
I didn't hear the phone. I must have been asleep.我刚才没有听到电话，我想必是睡着了。
4) must表示对过去某时正发生的事情的推测，must 后面要接不定式的完成进行式。
---Why didn't you answer my phone call ---Well, Imust have been sleeping, so Ididn't hear it.
5) 否定推测用can't。
If Tom didn't leave here until five o'clock, he can't be home yet.如果汤姆五点才离开这儿，他此时一定还未到家。
表示推测的用法 can, could, may, might, must 皆可表示推测，其用法如下：
1）情态动词+动词原形。
表示对现在或将来的情况的推测，此时动词通常为系动词。
I don't know where she is, she may be in Wuhan.
2）情态动词+动词现在进行时。
表示对现在或将来正在进行的情况进行推测。
At this moment, our teacher must be correcting our exam papers. 这时，我们老师想必在批改试卷。
3）情态动词+动词完成时。
表示对过去情况的推测。
We would have finished this work by the end of next December. 明年十二月底前我们很可能已完成这项工作了。
The road is wet. It must have rained last night. 地是湿的，昨天晚上一定下雨了。
4）情态动词+动词的现在完成进行时。 表示对过去正在发生事情的推测。
Your mother must have been looking for you. 你妈妈一定一直在找你。
5）推测的否定形式，疑问形式用can't, couldn't表示。 Mike can't have found his car, for he came to work by bus this morning. 迈克一定还没有找回他的车，因为早上他是坐公共汽车来上班的。
注意：could, might表示推测时不表示时态，其推测的程度不如can, may。
情态动词+have+过去分词
1) may(might) have + done sth, can (could) have + done sth表示过去，推测过去时间里可能发生的事情。
Philip may (might) have been hurt seriously in the car accident.
Philip can (could) have been hurt seriously in the car accident.
2)must have +done sth，对过去时间里可能发生的事情的推测，
语气较强，具有"肯定"，"谅必"的意思。
---Linda hasgone to work, buther bicycle is still here.
---She must have gone by bus.
3) ought to have done sth, should have done sth
本应该做某事，而事实上并没有做。否定句表示"不该做某事而做了"。
You ought to (should) have been more careful in this experiment.
He ought notto have thrownthe old clothes away.（事实上已扔了。）
ought to 在语气上比should 要强。
4) needn't have done sth本没必要做某事 I dressed very warmly for the trip, but Ineedn't have
done so. The weather was hot.
5) would like to have done sth本打算做某事
I would like to have read the article, but I was very busy then.
should和ought to
should 和ought to 都为"应该"的意思，可用于各种人称。
---Ought he to go ---Yes. Ithink he ought to.
表示要求，命令时，语气由 should（应该）、hadbetter最好）、 must（必须）渐强。
had better表示最好
had better 相当于一个助动词，它只有一种形式，它后面要跟动词原形。
Had better do sth had better not do sth
It is pretty cold. You'd better put on my coat.
She'd better not play with the dog. had better have done sth表示与事实相反的结果，意为"本来
最好"。 You had better have come earlier.
Would rather表示"宁愿" would rather do would rather not do
would rather… than…宁愿……而不愿。还有would sooner, hadrather, had sooner都表示"宁愿"、" 宁可"的意思。
If I have a choice, I had sooner not continue my studies at this school.
I would rather stay here than go home. = I would stay here rather than go home.
典型例题
----Shall we go skating or stay at home ----Which ___ do
A. do you rather B. would you rather C. will you rather D. should yourather
答案B。本题考查情态动词rather的用法，would rather +do sth 意为"宁愿"，本题为疑问句，would 提前，所以选B。
will和would would rather do would rather not do would rather… than…宁愿……而不愿。
还有would sooner, hadrather, had sooner都表示"宁愿"、" 宁可"的意思。
If I have a choice, I had sooner not continue my studies at this school.
I would rather stay here than go home. = I would stay here rather than go home.
典型例题
----Shall we go skating or stay at home ----Which ___ do
A. do you rathe rB. would you rather C. will you rather D. should you rather
答案B。本题考查情态动词rather的用法，would rather +do sth 意为"宁愿"，本题为疑问句，would 提前，所以选B。
need和dare
这两词既可做实义动词用，又可做情态动词用。作为情态动词，两者都只能用于疑问句，否定句和条件句。 need 作实义动词时后面 的不定式必须带to，而dare作实义动词用时, 后面的to 时常可以被省略。
1) 实义动词： need（需要,要求） need +n. / to do sth
2) 情态动词： need，只用原形need后加do，否定形式为need not。
Need you go yet Yes, Imust. / No,I needn't.
3) need 的被动含义：need, want, require, worth（形容词） 后面接doing也可以表示被动：
need doing =need to be done
专题：情态动词
（一）情态动词的定义: 情态动词表示说话人对某一动作或状态的态度。
（二）情态动词的特点:
1）有一定词义；2）不受主语人称和数的变化影响；3）与主要动词的原形（或称不带to的不定式）一起构成谓语（除ought to作固定词组看待）。
（三）情态动词的基本用法:
1. can (could)
1）表示能力，could主要指过去时间。
2）表示可能（理论上或是逻辑判断上）。
3）表示允许。
4）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。
5）比较委婉客气地提出问题或陈述看法。
2. may (might)
1）表允许，might可以指过去时间，也可指现在时间，语气更委婉。
在回答以may引起的问句时，多避免用这个词，而用其它方式，如Yes, please. / Certainly.
/ Please don’t ./ You’d better not. / No, you mustn’t.等，以免显得太严峻或不客气。
2）表可能（事实上）。可以指过去时间，也可以指现在时间，但语气更加不肯定。
3. must
1）表示义务。意为“必须”（主观意志）。
2）表示揣测。意为“想必、准是、一定”等，只用于肯定句。
4. shall
1）表征询意见，用于第一、第三人称疑问句。
2）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。
5. will
1）表意愿，用于各种人称陈述句。
2）表请求，用于疑问句。
3）表示某种倾向或习惯性动作。
6. should
1）表义务。意为“应该”（某件事宜于做），用于各种人称。
2）表推测，意为“想必一定、照说应该、估计”等。
7.would
1）表意愿。
2）表委婉地提出请求、建议或看法。
3）表过去反复发生的动作或过去的一种倾向。
8. ought to
1）表义务，意为“应该”（因责任、义务等该做），口气比should稍重。
2）表推测，暗含很大的可能，语气较弱。
9. used to
表示过去的习惯动作或状态，现在不复发生或存在。疑问式和否定式有两种。
（一）need和dare的用法
need和dare既可用作情态动词，也可用作实义动词。用作情态动词时，主要用于否定句和疑问句。用作实义动词时，可用于各种句式。
1.用作情态动词
2.用作实义动词
（二）情态动词后跟完成式和进行式的用法
1. 情态动词后跟完成式，表“应当已经……”，“想必已经……”，“本来可以……”等意。
2. 情态动词后跟进行式，表示“想必正在……”，“可能正在……”，“应当正在”等意。
（三）几组词的辨异
1. can 和be able to
1）情态动词can只有两种时态形式，现在式can和过去式could，而be able to有多种时态形式。
2）用在过去时中，could经常表示能够做某事，事实上不一定去做，而was ∕were able to则表示“过去做成了某事”。在否定句中两者可通用。
2. must和 have to
must表示主观意志，而have to表示由于客观因素不得不做某事。must没有过去式，除在间接引语中可用于表示过去时间，在直接引语中表示过去时间应该用had to代替。
3. would和used to
1）used to表示过去与现在或过去某时与后来的情况有不同，而would只表过去的情况。
2）used to可表示过去的习惯动作和经常的情况，而would只表示过去的习惯动作。