情态动词

第一节  概述

 

一、    常见的情态动词：

Can, could, may, might, shall, should, will, would, must, had better,

此外，还有些短语类似于情态动词的用法

Be able to (= can),

be going to (类似于will),

ought to,

be supposed to (类似于should)，

have to,

have got to (类似于must)，

再者，还有些词，如need, dare, 既可以做情态动词，也可以做实义动词

 

二、情态动词自身具有一定的含义，表示可能、建议、愿望、必要、允许、能力、怀疑等，

    以表达说话者对某种行为或状态的看法或态度。

 

三、情态动词在句子中不能单独作句子的谓语，必须和实意动词一起构成复合谓语。

 

 

第二节  情态动词用法

 

一、表示能力或可能： can, could, be able to

 

1. 现在或将来的能力

  Can 表示因为具备某些特点或条件，某人能够完成某事件或某事是可能存在的。

  即：“能力” 或“可能性”

Bob can play the piano. 后天获得的能力

John can lift that heavy box. 能力

A fish can’t walk, but they can swim. 天赋的能力

The theater can seat 10 million people. 可能

  注：表示现在的能力，一般不用 be able to

 

2. 过去的能力

   此时，could 即可以看作是can 的过去式，也可以表示许可、推测

Our son could talk when he was one year old.

I could run fast when I was a child, but now I can’t.

In those days few workers could support their families.

 

  表示过去的能力时，could 和were/ was able to 的区别：

 

    （1）表示过去“一般的能力，总的能力”，即在过去已经掌握，当时随时都可以实现的能力时，could和were/ was able to 都可以。

     I could / was able to recite several poems when I was 3 years of age. 我在三岁时就能背诵诗歌了。

     I could / was able to run fast when I was young, but now I can’t.

    

    （2）表示主语在过去某个特定场合所表现的“特定的能力，具体的能力”，或泛指某人在某一场合成功地完成了某件事，而非泛指的能力时，则用were/ was able to，相当于succeeded in doing, manage to do.

With the aid of the wood, he was able to swim across the river.

因为那块木头，他游到了河对岸。

I applied everywhere and finally I was able to get a good job.

He hurried to the station, and he was able to catch the train.

The fire spread through the building quickly but everybody was able to escape.

 

注：在否定句中，则可以使用could，与was/ were able to 互换。

    The two boys tried many ways to catch the fox, but they couldn’t succeed at last.

 

 

二、表示许可：permission

 

概述

（1）通常用陈述句表示许可。

（2）肯定的陈述句表示允许某人做某事；

否定的陈述句表示不允许某人做某事。

（3）常用的情态动词：may, might, can, could, be allowed to do…

 

1. 肯定句，表示给予许可

    I can leave the office as soon as I have finished. (= I am allowed to leave the office…)

You can use my car tomorrow.

——May I turn on the TV? (请求允许)

    ——Yes, of course you may.

 

2. 否定句，表示拒绝许可，甚至禁止

 ——May I turn on the TV? (请求允许)

    ——No, I am afraid you may not.

You can’t take your camera into the museum.

You can’t take the test paper out of the classroom.

 

 

3. could一般不表示现在的许可，而用来表示过去的许可。

  此时，相当于was/ were allowed to do

I could read what I liked when I was a child.

 

  如果表示过去允许进行某项特定的活动，我们要用was/ were allowed to do.

    Yesterday evening, Peter was allowed to watch TV for an hour.

 

  Could 更多用在陈述句中表示建议，在疑问句中表示请求。

 

 

三、表示请求：request.

 

（1）    表示请求，我们通常用一般疑问句

（2）    两种请求

A．主语用第一人称，表示请求对方许可我们做某事。同样，用陈述句表示许可，

用疑问句表示请求。

       Can I ask you a question?

       Yes, of course you can.

       May I?   

Could I？

　　Can I?

    Might I? （此种很少用）

    May I borrow your car?

 

    May I 和Could I表示正式的，非常礼貌地提出请求。

    Can I 是非正式地请求允许，一般与对方比较熟悉。

    Might I显得过于正式和客气，通常少用。

    典型回答：certainly, of course, sure

 

 

 

    B．主语用第二人称，表示请求对方为我们做某事。

 

Would you?

Could you?

Will you?

Can you?

Would you 和could you都表示很客气地请求对方。

Will you 则没有would you那样客气

Can、could you常用于非正式场合或熟人之间。

 

Would you please lend me your car?

Could you pass me the class, Rocky?

 

回答通常为：yes, I’d like to.

            Yes, I’d happy to.

            Yes, I’d be glad to.

            Certainly.

            Sure.

 

I am on duty this afternoon. Will you please cover for me? I have a doctor’s appointment.

今天下午我值班，你能替我吗？我得去看医生

I am sorry I can’t, my term paper is due tomorrow.

对不起我不能，我明天得交期末论文

 

四、 表示必须：necessity

Must, have to, have got to

 

1．Must 和have to 比较正式

All applicants must/ have to take an entrance exam.

 

2. have got to 比较口语化，got to在口语中经常被弱化成gotta

I have gotta go now, since I have a class in ten minutes.

 

3. 表示过去的必须，只能用had to或must

 

I had to/ must get up earlier last Sunday.

 

4. 否定形式：don’t have to: 不必要

            Mustn’t/ must not 千万不要

 

Tomorrow is Saturday, we don’t have to go to school.

You must not tell anyone my secret.

 

 

五、表示忠告或责任

Should, ought to, had better.

 

You should do as you are told.

We should study harder because the finals are near.

 

注：had better常用于口语中，后面加动词原形，

否定形式用 had better not to. 有一种警告或警示可能出现的恶果的意味。如

 

We had better study harder, or we’ll fail in the exam.

我们再不努力，考试就要挂了

 

 

六、表示建议

 

1. shall I/ we/ he…用于第一人称、第三人称的一般疑问句，表示征求对方的建议

Shall I open the window?

Shall he come with us?

Shall we leave at two?

 

2. could多用于肯定句，表示确定的建议。也可用can，语气更强烈。

——What shall we do this evening?

——We can/ could go to the cinema.

    We can/ could go for a walk since it’s a nice day,

 

3. may (just) as well/ might (just) as well

  表示推荐的更佳的方案，或建议换另一种方式来做某事

  翻译成“不放……”“莫不如……”

 

We may as well stay here tonight.

You might just as well wait till Wednesday and go by plane.

 

4.  let’s / why don’t (why not)

Let’s go to a movie.

Why don’t we go on a picnic?

 

注：should 表示强烈的、明确的忠告

Could 表示建议某事的可能性

 

He should see a doctor.

You could take a taxi.

Maybe John could pick you up.

 

 

七、shall的用法

 

1. shall 用于第二、第三人称的陈述句，表示说话人的许诺

You shall have the money back next week.

If he passes the exam he shall have a iPad.

 

2. shall 用于第二、第三人称的陈述句，表示说话人强烈的意愿，甚至威胁

You shall pay for this. 你一定得为此付出代价。

They shall do as they promised.

 

3. 法律条文，规章制度中，用shall表示必须，应当

    Ecah competitor shall wear a number

 

4. 用于第一、第三人称的一般疑问句表示建议。

 

Shall I buy you a ticket?

Shall we go now?

 

 

八、表示意愿，使用will或would

—— The phone is ringing.

—— I will get it.

 

 

九、表示过去重复动作，使用would/ used to

When I was a child, my mother would read/ used to read me a story at night before bad.

在我小的时候，妈妈总是在我睡觉前为我讲故事。

 

在表示过去反复发生的事情，或是习惯动作时，两者可以互换。

 

注（1）used to 往往含有“过去常常…但现在不再如此”的意味，

而would 则仅表示过去的重复的动作。

   （2）used to 也可表示过去的状体，would 则不能表示状态。

 

I used to have a cat.

There used to be a lot of fish in this river.

 

    （3）used to 和would 后面都不能接具体次数.

    I used to go to that restaurant over ten times when I was in college. (×)

 

 

 

十、 表示推测

 

1. 表示对现在推测的肯定句

  

   1.1 直接陈述事实，表示100%的确定

   —— Why isn’t John in class?

   —— He is sick.

 

   1.2 must表示强烈的肯定，90%的确定

   —— Why isn’t John in class?

   —— He must be sick

 

   1.3 may, could, might 用于较弱的肯定，没有太多的把握，少于50%的肯定

      在肯定语气中，三者差别不大。

在否定语气中，相对而言，couldn’t 比may not和might not 语气要强烈。

      He may be sick.= He might be sick.= He could be sick.

      He might be at the library.

      He could be out of town.

     

   1.4 can表示推测只能用在否定句和疑问句中

      You can’t buy shoes at the post office.

      此时，到底是判断上的“不能”，还是推测上的“应该不能”，只能按照语境来推理

 

 

2. 对现在推测的否定句

 

   2.1 直接描述，100%的否定。

      The restaurant is very bad since I never see anyone there.

 

   2.2 can’t, couldn’t, 强烈语气，表示说话者认为某事是不可能的。98%

      It couldn’t be very well since it is always empty.

 

   2.3 may not, might not, 一般的可能性，少于50%

      It may not be very good since it is empty now.

 

 

3. 对过去推测的肯定句：

   Must/ can/ may/ could/ might + 完成时

 

   3.1 直接陈述，表示100%的确定

      He was sick.

  

   3.2 must +完成时，95%的确定

      He must have been sick.

 

   3.3 may/ might/ could +完成时，少于50%的确定

      He may/ might/ could have been sick.

 

 

4. 对过去推测的否定句

   4.1 直接陈述，表示100%的确定。

      He wasn’t sick.

 

   4.2 couldn’t, can’t, 95%的确定

      He couldn’t have been sick.

      He can’t have been sick.

 

   4.3 may not/ might not, 少于50%的确定

      He may not have been sick.

      He might not have been sick.

 

 

5. 表示对将来的推测。

 

   5.1使用will进行直接陈述，表示100%的确定。

      Tomorrow John will take a test.

 

   5.2 should, ought to, 表示90%的确定。

      He should do well on the test since he works hard..

 

   5.3 may/ can/ might/ could + do,表示少于50%的确定。

      He can/ may/ might/ could do well on the test since he has failed for 5 times.

 

 

十一、 情态动词与完成式

 

1. 情态动词+完成式表示对过去的推测。

   Could have done, may have done, might have done, must have done

   Couldn’t have done, may not have done, might not have done, can’t have done.

 

      The money has disappeared! Who could have taken it?

      The situation was bad but it could have been worse.

      情况很糟，但本来很有可能更糟糕的。

      You screamed in your sleep last night, you must have had a terrible dream.

      Someone might have picked it up by mistake.

 

2. should/ ought to have done.

  表示过去应该做而没做的动作，含有批评的意思

     You should have phoned me last night.

  

用于否定句，则表示过去不应该做的事，而实际上做了。也含有批评的意思。

    You shouldn’t have eaten so much yesterday, at least, not that much.

 

  有时，也用could have done来表示批评的含义。

      You could have told me you were getting married.

      你结婚应该告诉我啊！

 

      I could have lent you the money, why didn’t you ask me?

      我可以借给你钱的啊！为什么不问我借啊？

 

3. needn’t have done.

  本来不必做的事，实际上做了。

      You needn’t have gone to the meeting since it had been cancelled.

      The restaurant was nearly empty, we needn’t have book the table.

 

小结：

情态动词用法一览表

情态动词	基本用方法	例句
Can	表示能力	Bob can play the piano, while I can’t.
	用于肯定句或否定句中 表示许可	You can leave the office now. You can’t leave without saying a word.
	用于疑问句中，表示请求	Can I borrow your car tonight?
	用于否定句，表示不可能	You can’t see her now because she is out.
could	表示过去的能力	John could talk when he was two years old
	表示委婉地有礼貌地请求	Could you show me the way?
	表示少于50%的推测	Look at those dark clouds. It could start raining any minute.
	提出建议	We could have a walk since you have recovered.
may	礼貌地请求	May I use your book?
	正式地允许	You may take my book.
	少于50%的推测	He may be waiting at the station when we arrive.
might	少于50的推测	Tom might not know Rocky’s address.
	委婉的请求（很少使用）	Might I kiss your baby?
will	100%的确定	I believe he will do well in tomorrow’s test.
	意愿，打算	——The phone is ringing. ——I will get it.
	礼貌地请求	Will you open the window?
would	礼貌地请求	Would you please close it now?
	过去的重复的动作	When I was a child, I would go to school with her ever day
Used to	过去的重复的动作	I used to talk with my little dog every night.
	表示过去存在的某种情况	There used to be a river here.
shall	第一第三人称的一般疑问句 表示“建议”	Shall I open your gift?
	强烈要求	They shall do as they are told.
	承诺	You shall have the money back next week.
should	表示劝告	Drivers should obey the speed limit.
	对将来90%确定的推测	He should do well on the test.
Ought to	表示劝告	Drivers ought to obey the speed limit.
	对将来90%确定的推测	He ought to do well on the test.
Had better	表示劝告	You had better go now.
must	强烈语气	I must study hard.
	用于否定句，表示禁止	You must not cheat on the exam
	95% 的确定	He must be sick.
Have to	表示必须	I have to go now.
	口语陈述句中，可用have got to	I have got to leave now.