情态动词（高一新课讲解）.doc

情态动词
I 情态动词的定义
情态动词是一种本身有一定的词义，表示说话人的情绪、态度或语气的动词，但不能单独作谓语，只能和其他动词原形构成谓语。
情态动词数量不多，但用途广泛，主要有： can (could), may (might), must, need, ought to, dare (dared), shall (should), will (would) .
II 情态动词的位置
情态动词在句中放在谓语动词之前，谓语动词前若有助动词，则在助动词之前，疑问句中， 情态动词放在主语之前。
• I can see you. Come here. 我能看见你，过来吧。
• He must have been away. 他一定走了。
• What can I do for you? 你要什么？
• How dare you treat us like that! 你怎么敢那样对待我们!
Ⅲ 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，后面只能接动词原形。
　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。
Ⅳ 情态动词的用法
A. can; could; be able to
can
1. 表示“能力”(此时过去时是could)
What can you do?
2. 表示许可、请求，“可以”。 在口语中，can可以代替may表示许可，而may比较正式。（此时用could或might语气更委婉）
--Can/Could I go now?
--Yes, you can.
3 表示推测（否，疑），把握很大,could也可表推测（肯，否，疑）,把握比can小。
--Look! Someone is coming! Who can it be?
--It can’t be him. He has gone to Paris.（不可能）
He could be here soon. 他很快就来。
4 表示感情（惊异/不耐烦）“究竟，到底”（主要用于否定句，疑问句和感叹句中。）
How can you be so foolish?
What can it possibly be? 到底那是怎么一回事?
They can’t be working at this time of day.
5 肯定句中客观存在的可能性。“有时会，偶尔”
It can be quite windy there, especially in spring.
Could
1.表示能力， can 的过去式，过去能够
Could you speak English then? 那时候你会说英语吗?
Looking down from the plane, we could see lights on the runway.
从飞机上向下看，我们可以看见机场跑道上的点点灯火。
2. 请求允许（委婉语气）（问句的答语不用could，而用can）
Could [Can] I use your pen? ” “Yes, of course you can.”/ No, I’m afraid not.
3. 表示推测可能性（肯，否，疑）
We could go there this summer. 今年夏天我们可能要去那儿。(将来可能性)
You could be right, but I don’t think you are.你可能是对的，但我并不认为你是对的.(现在可能性)
4. could have done ① 对过去推测，可能已经……
② 本来能够却没做，差点就
He can’t [couldn’t] have seen her there. 他不可能在那儿见到她。
He could have gone home. 他可能已回家了
He could have told her, but he didn’t choose to. 他本来可以告诉她的，但他却没有。
You could have asked me before you use my phone. 你打电话之前本来可以问我一声。
I was so angry that I could have killed him. 我是那样生气，差点把他杀了。
★ can 和 be able to 都可以表示能力，意思上没什么区别，但can 只有现在式和过去式(could)，而be able to 则有更多的形式。
过去时：were/was able to
将来时：will/shall be able to
完成时：have /has been able to
★ 如果要表达将来的能力时，一般要用 will/shall be able to．
• No one is able to do it.
• We shall be able to finish the work next week.
• I haven’t been able to finish the book
★ could与 was/ were able to的区别：could 只表有能力， was/were able to 意含”过去某时经过努力设法做成了某事”, 还可以表示结果
They worked hard, so they were able to do more for the company.
He could cure the old man’s illness. (能治好)
He was able to cure the old man’s illness. (治好了)

B. may 和 might
may （过去式might）
1. 表示允许﹑许可，might提问更委婉。口语中可用can/ could.
• ---May/Might I watch TV after supper?
---Yes, you may./ Yes, please./ Certainly.
---No, you mustn't. / No, you may not. / No, you can’t.
---No, you’d better not.
2. 表示推测(肯，否)，有“或许”、“可能”的意思。might把握更小。疑问句用can/ could
• He may be right.
• I hear there may be a few copies left.
• He may come today (tomorrow).
• He might come today (tomorrow).
3. 表示祝愿，倒装。
May you succeed !
May you have many more days as happy as this one.
might
1. may 的过去式
He said that I might borrow this book.
2. 许可(委婉语气) Might I ...
3. 表示推测（肯，否） “或许”“可能”把握比may小。疑问句用can/could
He might get there in time, but I’m not sure.
★ may [might] (just) as well + do
意为“不妨”、“还是…为好”等，用 might 比用 may 语气更委婉。如：
I’m ready，so I might as well go now．我已准备好，因此不妨现在就走。
There’s nothing to do, so I may [might] as well go to bed.
★ may well... 完全可能

C. must, have to
must
1. must 表示“必须”。否定式must not (mustn’t)表示“不应该”、“不许可”、“不准”、“禁止”等。
• Everybody must obey the rules.
• The work must be finished as soon as possible.
• You mustn’t lend it to others.
• You mustn’t speak like that to your mother.
★ 在回答有“must” 的询问时，否定式常用need not (needn’t) / don’t have to表示“不必”, 而不用must not, 因为must not 表示“禁止”“不可以”
--- Must I go now? --- Yes, you must.
---No, you needn’t. / No, you don’t have to.
2. must 表示推测（“一定”、“必定”），只用在肯定句中, 其否定形式为can’t，表示“不可能”
• You must be hungry after the long walk.
• The Chinese language must have the large number of speakers.
3. must 表示说话人不耐烦的态度，“干嘛偏要”
----- ____you make so much noise?
----- Sorry, I will take care not to.
A Must B Can C May D Would
★ must + have + done，表示对过去事物的肯定推测。 “一定做过...”
He must have told my parents about it. 他一定把这件事情告诉我父母亲了。
★ must表示推测时，其反意疑问句应根据动词的实际时态而变化。如：
§ It must be nice to take a walk here, isn’t it?
§ Tom buys a lot of apples ,he must like eating them, doesn't he？
§ He must have passed the examination , hasn’t he ?
Must have done 的反意疑问句有三种情况:
①从句中含有过去的时间状语 , 反意疑问句用过去时.
§ The ground is wet . it must have rained last night, didn’t it?
②从句中含有过去完成时的时间状语 ，反意疑问句用过去完成时.
§ By the end of last term, we must have learnt 2000 words, hadn’t we?
③若从句中不含任何时间状语 ，反意疑问句用现在完成时
§ We must have met somewhere, haven’t we?
★ must 表示“必须”　“有必要”时，反意疑问句部分用mustn’t...? 或 needn’t ...?　
You must go home right now, needn’t you?
★ must 用否定形式 mustn’t时，附加疑问句部分用may或must…?
You mustn’t cheat in the examination, must you?
4. must 和 have to 的区别： must 表示说话人的主观看法, have to “不得不, 必须”，表示客观需要、客观条件只能如此。have to 比 must 有更多形式。mustn’t表示“决不能，禁止，一定不要”，而don’t have to表示“不必要”．（英国英语常用needn’t) .
• I don’t like the TV set. I must buy a new one. （主观看法）
• The TV set is broken. I have to buy a new one. （客观需要）
• He had to spend his childhood in hard work, helping his father on their small farm.
• You will have to do it again。(将来)

D. ought to/ should/ shall
ought to
ought to用于反映客观情况或涉及义务和规定时，常译作“应该”、“应当”(和should差不多， 只是语气较强)，有时表示非常可能的事情。
• There ought not to be much noise in a hospital.
• --- Ought he to go? --- Yes, he ought to.
• If she is completely well, she ought to be back at school today.
ought to have done指过去动作,表示一件事情该做而未做。
ought not to have done 表示一件不该做的事情却做了。
should
1. 用于表示劝告和建议，“应该”．表示自己的主观看法,语气比ought to弱。
You should keep your promise.
★ should + have done 指过去动作,表示一件事情该做而未做。
should not + have done 表示一件不该做的事情却做了。
--- Who did it sound like? Anybody you know?
--- Well, perhaps Jeff. I should have asked who was calling before he hung it up.
2. 表推测，“按道理，按常理应该”
They should have arrived by two o’ clock.
3. 表示惊讶,赞叹，不满，责备 “竟然”
I am sorry that you should do such a thing.
4. 用于if引导的虚拟条件句中，表示一件事听起来可能性小，但也不是完全不可能。有“万一”的意思
Should I be free tomorrow, I’ll come
Ask Tom to ring me up if you should see him.
shall
1. shall 作为情态动词，用于第二、第三人称，陈述句，表示说话人的意愿，有“命令”、“警告”、“威胁”、“强制”、“允诺”等意思。“必须，应，可以”．
• You shall do as I say. （命令）
• Tell him that he shall have the book tomorrow. （允诺）
• You shall be punished if you break the law. (表警告)
2. 用于第一、第三人称, 在疑问句中，shall 用来征询对方意见。“……好吗？”“要不要……？”
• Where shall I wait for you?
• Shall he come at once?
• Shall we start the meeting now?
3.在条约﹑规定﹑法令等文件中表示义务或规定，用于第三人称
The new regulation shall take effect on June 1st。

E. will 和 would
will
(1) will 表示“意志”、”决心” 、“意愿”，可用于多种人称。will 指现在，would 指过去。
• I will tell you all about it.
• He won’t go.
(2) will 在疑问句中用于第二人称时，表示询问对方的意愿或向对方提出请求.委婉语气would
• I’m going to go shopping after school. Will you go with me?
• Will you please give him a message when you see him?
(3) 表示习惯动作，有“总是”、“惯于”的意思。过去式would
He’ll talk for hours if you give him the chance.
(4) 表示功能，“能”
The door won’t open. / The car won’t start.
(5) 用于叙述真理,客观规律时“会”
Oil will float on water. / Fish will die without water.
would
(1) would是will的过去式，表示过去时间的“意愿”、“愿望”，用于多种人称。
• They said that they would help us.
• I promised that I would do my best.
(2) 表示说话人的意愿或向对方提出请求，语气比will 委婉。指的是现在时间。
• Would you like some bananas?
• I’d like to see your new bicycle.
• --- Would you like to see a film? --- Yes, I’d like to.
• --- Thanks. I’m afraid not. / I’m afraid I won’t be able to.
(3) 表示过去的习惯动作。
• She would sit like that for hours.
• Everyday she would get up at six o’clock and light the fire.
★ would和used to区别：
would “过去常常”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，不能说：She would be a quiet girl.
used to 则着眼于过去和现在的对比，隐含“现在已不复如此”之意，动作或状态都可表示．She used to be a quiet girl.
When young, he would go out for a trip on Sundays. (Now maybe still does)
When young, he used to go out for a trip. (But now he doesn’t)
Near the village, there _____ be a stream.
A. would B. used to

F. need 和 dare
1. need 表示“需要”、“必须”。通常用在否定句或疑问句中。
• He needn’t pay for it.
• --- Need you go now? --- Yes, I must. --- No, I needn’t.
2. dare 表示“敢”。通常用于否定句、疑问句、条件从句和if/whether 引出的宾语从句中。
• How dare you say I’m unfair?
• She dare not do so.
• He asked me if I dared speak English in public.
★ need 和 dare 也可用作行为动词，变化与一般动词相同
• She didn’t need to go.
• --- Who dares to go? - -- I don’t dare (to) go.
★ I dare say …作插入语,我想, 大概, 可能, 或许
★ “needn‘t + have done” 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。

G. had better/ had best “最好”，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

Ⅴ. 情态动词+ have done
must have done,“一定做过/一定已经．．．”，表示对过去情况极大把握地推测，仅用于肯定句
may/might have done 也许做过某事 may/ might not have done 也许没做过某事(之用肯、否)
might have done 本来可以做某事却没做
can与have done 连用时, 为否定句或疑问句,对过去的推测“不可能，一定没做过某事”
could have done本来可以做某事却没做
needn’t have done 表示”本来不必做(却做了)”而needn’t do 则表示”不必做(也没做)”
ought to /should have done 表示”本来应当做的却没做”
oughtn’t / shouldn’t have done 本来不应该做某事却做了
would/could/might/should + have done 用来表示与过去事实相反的虚拟语气
would rather have done 表示”当时宁愿做了某事”，否定形式：would rather not have done
eg. If I had been free that day, I would rather have gone with you.
would like/love to have done 表示” 本想做某事” 而实际上未做。

★情态动词+be doing 表示推测现在正在进行或可能正在进行的动作。
eg. His mother must be waiting at the school gate.
情态动词+be done 表示现在或将要发生的被动的动作。
eg. Men must not be judged by their looks.
情态动词+have been done 表示对过去已经发生的被动动作的猜测，有时含有指责，抱怨等不满的情绪。
eg. I can’t find my recorder . it may have been taken away by someone.
情态动词+have been doing 表示根据猜测，从过去到现在一直在进行的动作，具有“应该一直在……”或“想必一直在……”等意思。
eg. They may have been discussing the problem this morning .

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