情态动词：can may must的用法情态动词：can may must麻烦大家帮忙详细讲一下

情态动词：can may must的用法情态动词：can may must麻烦大家帮忙详细讲一下
情态动词：can may must的用法
情态动词：can may must
麻烦大家帮忙详细讲一下

情态动词：can may must的用法情态动词：can may must麻烦大家帮忙详细讲一下
情态动词有can (could), may (might), must, have to, shall (should, will (would), dare (dared), need (needed), ought to等. 情态动词无人称和数的变化；不能单独使用,必须与其后的动词原形构成谓语
一、 can, could
1) 表示能力（体力、知识、技能）.
Can you lift this heavy box?（体力）
Mary can speak three languages.（知识）
Can you skate?（技能）
此时可用be able to代替.Can只有一般现在时和一般过去式；而be able to则有更多的时态.
I’ll not be able to come this afternoon.
当表示“经过努力才得以做成功某事”时应用be able to,不能用Can.如：
He was able to go to the party yesterday evening in spite of the heavy rain.
2) 表示请求和允许.
-----Can I go now?
----- Yes, you can. / No, you can’t.
此时可与may互换.在疑问句中还可用could,
might代替,不是过去式,只是语气更委婉,不能用于肯定句和答语中.
---- Could I come to see you tomorrow?
---- Yes, you can. ( No, I’m afraid not. )
3) 表示客观可能性（客观原因形成的能力）.
They’ve changed the timetable, so we can go by bus instead.
This hall can hold 500 people at least.
4) 表示推测（惊讶、怀疑、不相信的态度）,用于疑问句、否定句和感叹句中.
Can this be true?
This can’t be done by him.
How can this be true?
二、 may, might
1) 表示请求和允许.might比 may语气更委婉,而不是过去式.否定回答时可用can’t
或mustn’t,表示“不可以,禁止”.
----Might/ May I smoke in this room?
---- No, you mustn’t.
---- May/Might I take this book out of the room?
---- Yes, you can. (No, you can’t / mustn’t. )
用May I...?征徇对方许可时比较正式和客气,而用Can I...?在口语中更常见.
2）用于祈使句,表示祝愿.
May you succeed!
3) 表示推测、可能性（不用于疑问句）.
might不是过去式,它所表示的可能性比may小.
1．He may /might be very busy now.
2．Your mother may /might not know the truth.
三、 must, have to
1) 表示必须、必要.
You must come in time.
在回答引出的问句时,如果是否定的,不能用mustn’t（禁止,不准）,而用needn’t, don’t have to（不必）.
---- Must we hand in our exercise books today?
---- Yes, you must.
---- No, you don’t have to / you needn’t.
2) must是说话人的主观看法, 而have to则强调客观需要.Must只有一般现在时, have to 有更多的时态形式.
1． he play isn’t interesting, I really must go now.
2． I had to work when I was your age.
3) 表示推测、可能性（只用于肯定的陈述句）
1． You’re Tom’s good friend, so you must know what he likes best.
2． Your mother must be waiting for you now.
四、 dare, need
1) dare作情态动词用时, 常用于疑问句、否定句和条件从句中, 过去式形式为dared.
1． How dare you say I’m unfair?
2． He daren’t speak English before such a crowd, dare he?
3． If we dared not go there that day, we couldn’t get the beautiful flowers.
2) need 作情态动词用时, 常用于疑问句、否定句.在肯定句中一般用must, have to, ought to, should代替.
1．You needn’t come so early.
2. ---- Need I finish the work today?
---- Yes, you must. / No, you needn’t.
3) dare和 need作实义动词用时, 有人称、时态和数的变化.在肯定句中,dare后面常接带to的不定式.在疑问句和否定句中,dare后面可接带to或不带to的不定式.而need后面只能接带to的不定式.
1. I dare to swim across this river.
2. He doesn’t dare (to) answer.
3. He needs to finish his homework today.
五、 shall, should
1) shall 用于第一人称,征求对方的意见.
What shall we do this evening?
2) shall 用于第二、三人称,表示说话人给对方的命令、警告、允诺或威胁.
1. You shall fail if you don’t work hard.(警告)
2. He shall have the book when I finish it.(允诺)
3. He shall be punished.(威胁)
六、 will, would
1) 表示请求、建议等,would更委婉.
Will / Would you pass me the ball, please?
2) 表示意志、愿望和决心.
1. I will never do that again.
2. They asked him if he would go abroad.
3) would表示过去反复发生的动作或某种倾向.would表示过去习惯时比used to正式,且没有“现已无此习惯”的含义.
1. During the vacation, he would visit me every other day.
2. The wound would not heal.
4) 表示估计和猜想.
It would be about ten o’clock when she left home.
七、 should, ought to
1) should, ought to表示“应该”,ought to表示义务或责任,比should语气重.
1. I should help her because she is in trouble.
2. You ought to take care of the baby.
2) 表示劝告、建议和命令.should, ought to可通用,但在疑问句中常用should.
1. You should / ought to go to class right away.
2. Should I open the window?
3) 表示推测
should , ought to (客观推测), must(主观推测).
1.He must be home by now. (断定他已到家)
2.He ought to/should be home by now.(不太肯定)
3. This is where the oil must be.(直爽)
4. This is where the oil ought to/should be.(含蓄)
八、 情态动词+不定式完成式（have done）
1) can / could + have done在肯定句中表示“本来可以做而实际上能做某事”,是虚拟语气；在疑问句或否定句中表示对过去行为的怀疑或不肯定, 表示推测.
1. You could have done better, but you didn’t try your best. （虚拟语气）
2. He can’t have been to that town.（推测）
3. Can he have got the book?（推测）
2) may / might +不定式完成式（have done）
表示对过去行为的推测.不能用于疑问句中,没有虚拟语气的用法.Might所表示的可能性比may小.
1. He may not have finished the work .
2. If we had taken the other road, we might have arrived earlier.
3）must +不定式完成式（have done）
用于肯定句中,表示对过去行为的推测.意为“一定、想必”.其疑问、否定形式用can,can’t代替.参看1) can / could + have done表示推测.
1. You must have seen the film Titanic.
2. He must have been to Shanghai.
4）should +不定式完成式（have done）
用于肯定句中,表示对过去行为的推测.
He should have finished the work by now.
表示“本应该做而实际上没有做某事”,其否定式表示某种行为本不该发生却发生了.可以与ought to +不定式完成式（have done）互换.
1. You ought to / should have helped him. (but you didn’t.)
2. She shouldn’t have taken away my measuring tape, for I wanted to use it.
5) needn’t +不定式完成式（have done）
表示“本来不必做而实际上做了某事”.
You needn’t have watered the flowers, for it is going to rain.
6) will +不定式完成式（have done）
主要用于第二、三人称,表示对已完成的动作或事态的推测.
He will have arrived by now.
参考资料：http://www.qgwz.com/article/class171/class174/200509/115.html

can may must 都是情态动词，后面加动词原形！

情态动词有can (could), may (might), must, have to, shall (should, will (would), dare (dared), need (needed), ought to等。 情态动词无人称和数的变化；不能单独使用，必须与其后的动词原形构成谓语
一、 can, could
1) 表示能力（体力、知识、技能）。
Ca...

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情态动词有can (could), may (might), must, have to, shall (should, will (would), dare (dared), need (needed), ought to等。 情态动词无人称和数的变化；不能单独使用，必须与其后的动词原形构成谓语
一、 can, could
1) 表示能力（体力、知识、技能）。
Can you lift this heavy box?（体力）
Mary can speak three languages.（知识）
Can you skate?（技能）
此时可用be able to代替。Can只有一般现在时和一般过去式；而be able to则有更多的时态。
I’ll not be able to come this afternoon.
当表示“经过努力才得以做成功某事”时应用be able to，不能用Can。如：
He was able to go to the party yesterday evening in spite of the heavy rain.
2) 表示请求和允许。
-----Can I go now?
----- Yes, you can. / No, you can’t.
此时可与may互换。在疑问句中还可用could,
might代替，不是过去式，只是语气更委婉，不能用于肯定句和答语中。
---- Could I come to see you tomorrow?
---- Yes, you can. ( No, I’m afraid not. )
3) 表示客观可能性（客观原因形成的能力）。
They’ve changed the timetable, so we can go by bus instead.
This hall can hold 500 people at least.
4) 表示推测（惊讶、怀疑、不相信的态度），用于疑问句、否定句和感叹句中。
Can this be true?
This can’t be done by him.
How can this be true?
二、 may, might
1) 表示请求和允许。might比 may语气更委婉，而不是过去式。否定回答时可用can’t
或mustn’t，表示“不可以，禁止”。
----Might/ May I smoke in this room?
---- No, you mustn’t.
---- May/Might I take this book out of the room?
---- Yes, you can. (No, you can’t / mustn’t. )
用May I...？征徇对方许可时比较正式和客气，而用Can I...？在口语中更常见。
2）用于祈使句，表示祝愿。
May you succeed!
3) 表示推测、可能性（不用于疑问句）。
might不是过去式，它所表示的可能性比may小。
1．He may /might be very busy now.
2．Your mother may /might not know the truth.
三、 must, have to
1) 表示必须、必要。
You must come in time.
在回答引出的问句时，如果是否定的，不能用mustn’t（禁止，不准），而用needn’t, don’t have to（不必）.
---- Must we hand in our exercise books today?
---- Yes, you must.
---- No, you don’t have to / you needn’t.
2) must是说话人的主观看法， 而have to则强调客观需要。Must只有一般现在时， have to 有更多的时态形式。
1． he play isn’t interesting, I really must go now.
2． I had to work when I was your age.
3) 表示推测、可能性（只用于肯定的陈述句）
1． You’re Tom’s good friend, so you must know what he likes best.
2． Your mother must be waiting for you now.
四、 dare, need
1) dare作情态动词用时, 常用于疑问句、否定句和条件从句中, 过去式形式为dared。
1． How dare you say I’m unfair?
2． He daren’t speak English before such a crowd, dare he?
3． If we dared not go there that day， we couldn’t get the beautiful flowers.
2) need 作情态动词用时, 常用于疑问句、否定句。在肯定句中一般用must, have to, ought to, should代替。
1．You needn’t come so early.
2. ---- Need I finish the work today?
---- Yes, you must. / No, you needn’t.
3) dare和 need作实义动词用时， 有人称、时态和数的变化。在肯定句中，dare后面常接带to的不定式。在疑问句和否定句中，dare后面可接带to或不带to的不定式。而need后面只能接带to的不定式。
1. I dare to swim across this river.
2. He doesn’t dare (to) answer.
3. He needs to finish his homework today.
五、 shall, should
1) shall 用于第一人称，征求对方的意见。
What shall we do this evening?
2) shall 用于第二、三人称，表示说话人给对方的命令、警告、允诺或威胁。
1. You shall fail if you don’t work hard.(警告)
2. He shall have the book when I finish it.(允诺)
3. He shall be punished.(威胁)
六、 will, would
1) 表示请求、建议等，would更委婉。
Will / Would you pass me the ball, please?
2) 表示意志、愿望和决心。
1. I will never do that again.
2. They asked him if he would go abroad.
3) would表示过去反复发生的动作或某种倾向。would表示过去习惯时比used to正式，且没有“现已无此习惯”的含义。
1. During the vacation, he would visit me every other day.
2. The wound would not heal.
4) 表示估计和猜想。
It would be about ten o’clock when she left home.
七、 should, ought to
1) should, ought to表示“应该”，ought to表示义务或责任，比should语气重。
1. I should help her because she is in trouble.
2. You ought to take care of the baby.
2) 表示劝告、建议和命令。should, ought to可通用，但在疑问句中常用should。
1. You should / ought to go to class right away.
2. Should I open the window?
3) 表示推测
should , ought to (客观推测), must(主观推测)。
1.He must be home by now. (断定他已到家)
2.He ought to/should be home by now.(不太肯定)
3. This is where the oil must be.(直爽)
4. This is where the oil ought to/should be.(含蓄)
八、 情态动词+不定式完成式（have done）
1) can / could + have done在肯定句中表示“本来可以做而实际上能做某事”，是虚拟语气；在疑问句或否定句中表示对过去行为的怀疑或不肯定, 表示推测。
1. You could have done better, but you didn’t try your best. （虚拟语气）
2. He can’t have been to that town.（推测）
3. Can he have got the book?（推测）
2) may / might +不定式完成式（have done）
表示对过去行为的推测。不能用于疑问句中，没有虚拟语气的用法。Might所表示的可能性比may小。
1. He may not have finished the work .
2. If we had taken the other road, we might have arrived earlier.
3）must +不定式完成式（have done）
用于肯定句中，表示对过去行为的推测。意为“一定、想必”。其疑问、否定形式用can，can’t代替。参看1) can / could + have done表示推测。
1. You must have seen the film Titanic.
2. He must have been to Shanghai.
4）should +不定式完成式（have done）
用于肯定句中，表示对过去行为的推测。
He should have finished the work by now。
表示“本应该做而实际上没有做某事”，其否定式表示某种行为本不该发生却发生了。可以与ought to +不定式完成式（have done）互换。
1. You ought to / should have helped him. (but you didn’t.)
2. She shouldn’t have taken away my measuring tape, for I wanted to use it.
5) needn’t +不定式完成式（have done）
表示“本来不必做而实际上做了某事”。
You needn’t have watered the flowers, for it is going to rain.
6) will +不定式完成式（have done）
主要用于第二、三人称，表示对已完成的动作或事态的推测。
He will have arrived by now.

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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 i...

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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 has gone to work, but her 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 not to have thrown the 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 I needn'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.
参考资料：http://www.52en.com/whbm/grammar/index.htm
回答者：zhangsong045 - 童生 一级 4-10 21:00
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归纳总结:情态动词用法ABC
情态动词表示说话人对某一动作或状态的态度,或表示主观设想。情态动词有自己的词义,但不能单独作谓语动词,必须和后面的动词连用构成谓语,没有人称和数的变化。常用的有can, may, must, need等。情态动词是中考测试的重点,准确把握情态动词在具体语境中所表达的意义至关重要。
一、can的用法
1.表示能力,有"能"、"会"、"能够"的意思。例如:
Can you drive a car?
2.表示可能,常用于否定句或疑问句。例如:
Can it be true?
Today is Sunday. He can't be at school today.
3.表示允许,口语中代替may,有"可以"的意思。例如:
You can use my car.
4.can和be able to 的区别:
can表示能力时,可以用be able to代替;can只有can和could两种时态,而be able to可用于其他时态;be able to强调"通过努力有能力做到",如果表示"某事已经成功"应用 be able to,而不用could。例如:
He was able to leave Europe before the war began.
二、may的用法
1.表示许可(否定回答用can't或mustn't)。例如:
-May I take the magazine out of the reading room?
-No, you can't (mustn't).
2.表示可能,通常只用于陈述句中。例如:
It may rain this afternoon.
3.表示祝愿,用于祈使句中。例如:
May you have good luck!
三、must的用法
1.表示必须、应该(否定形式用needn't或don't have to )。例如:
-Must I finish the work before dark?
-No, you needn't / don't have to. You may leave it for tomorrow.
2.must not (mustn't)表示强烈禁止。例如:
You mustn't get to school late.
3.表示推测,只用在肯定句中,"一定"、"想必"之意。其否定意义"不可能",用can't be形式。例如:
-The light in her room is still on; she must be at home now.
-She can't be at home. I saw her out just ten minutes ago. She forgot to turn off her light.
4.must和have to的区别:
must表示说话人的主观看法;而have to强调客观情况迫使人不得不……;must只能表示现在"必须",表示过去的事情要用had to;have to有时态、人称和数的变化。must和have to的否定意思不同。比较:
You mustn't do that.(你千万不能做那件事。)
You don't have to do that.(你不必做那件事情。)
四、 need的用法
need作情态动词时表示"需要",主要用于否定句和疑问句。例如:
-Need we finish the work today?
-Yes, you must. / No, you needn't.

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