情态动词及虚拟语气讲解

情态动词

结构图概述

can和could的用法

may和might的用法

must的用法

need和dare的用法

情态动词基本用法shall和should的用法

will和would的用法

ought to的用法

used to的用法

had better与would rather的用法

情态动词m u s t,c a n,c o u l d,m a y,m i g h t

其它用法表推测的用法

“情态动词+have+done” 结构的含义及用法

一、概述：情态动词有：can(could)，may(might)，must(must)，have to，

shall(should)，will(would)，need(need)，dare(dared)，ought to.情态动词无人称和数的变化，不能独立使用．它与其后边的动词原形一起构成谓语．情态动词的具体用法如下:

二、情态动词的用法：

(一) can和could的用法

l. 注意can和could的一般疑问句的回答（could用在疑问句中比can语气更委婉）。如:

Can you finish this work tonight---Yes，I can./No，I can't.

Could you help me---Sure./Certainly./ course.或Yes，I can. /No（或Sorry），I’m afraid not.

2. can和could表示推测（见后面）。

3. can与be able to的区别：

①can常常指某人具备某种知识或技能，而be able to则指具体做某件事的能力。如：

I can read，but I am not able to read this passage.

②can常常只有现在或过去两种形式，而be able to可以有多种形式，可以用于多种时态。如：

Jim can read and write now，but he couldn’t do it when he was four years old.

At that time he was able to answer the question，now he is able to answer the question too. Of course he will be able to answer such question easily in the future.

(二) may和might的用法

1．注意may与might的一般疑问句的回答（might用在疑问句中比may语气更委婉）。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。如: May/Might I ask you some questions

---Yes，you may./Yes，you can./Yes，you must./Yes，please.

---No，you may not.（一般不常用）/No，you can't./No，you mustn't./No，you'd better not.

2. may和might表示推测（见后面）。

3. 用于祈使句中表示祝愿．例如：

May you succeed!

(三) must的用法：

1.注意must的一般疑问句的回答：

Must I go there at once---Yes，you must./No，you needn't.=No，you don’t have to.

表示推测（见后面）。

与have to的区别：

① must只有一种形式，而have to有各种形式和时态，随have的变化而定。

②must表示的是说话人的主观看法，而have to则往往强调客观需要．例如：The play is not interesting. I really must go now. I have missed the bus，so I have to walk home. I had to work when I was your age.

(四) need和dare的用法

1．作情态动词：

need表示“需要”或“必须”，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（注意其一般疑问句的回答方式与must完全一样）；dare主要用于疑问句、否定句和条件状语从句中，一般不用于肯定句。例如：

You needn’t come so early.

Need I finish her work today ---Yes，you must./No，you needn't.=No，you don’t have to.

Dare he do it---No，he daren’t. How dare you say I’m unfair．If you dare come here，I will come to meet you. He daren’t speak English before such a crowd，dare he---Yes，he dare./No，he daren’t.

注意：needn’t have done“表示本来不必做某事而实际上却做了某事”。例如：You needn’t have waited for me．

2. 作实义动词：

dare和need后面接不定式（to do），有人称、数和时态的变化，变否定句和疑问句时要借助于助动词。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；而在否定和疑问句中，dare后面的不定式可以不带to．例如：

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．Does he dare to go

there---Yes，he does./No，he doesn’t. He needs to finish it this evening．He

doesn’t need to finish it this evening. Does he need to finish it t his evening---Yes，he does./No，he doesn’t.

(五) shall和should的用法。

的用法：

①shall用于第一人称的肯定句表示将来，用于第一人称的特殊疑问句表示征求对方的意愿．例如：

I shall go to Beijing tomorrow. What shall we do this evening

②shall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提出请示。例如：

Shall we begin our lesson When shall he be able to leave the hospital

③shall用于第二、三人称的肯定句中，表示说话人给对方的命令、警告、允诺或威肋．例如：

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)

2. should的用法：

①sho uld的用法：

a. should表示劝告、建议、命令，其同义词是ought to．如：

You should go to class right away. Should I open the window

可以用在if引导的条件从句中，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。例如：

Ask her to ring me up if you should see her.你万一见到她，请让她绘我打个电话。

If you should change your mind，please let us know．万一你改变主意，请通知我们。

Should I( if I should) be free tomorrow I will come.万一我明天有时间，我就来。

c.“Why/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”。例如：Why should you be so late today你今天怎么来得这么晚

Where is Betty living 一How I should know - 贝蒂住在哪里- 我怎么会知道呢

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。

d.“ should have done”表示本应该做到而实际上没有做到．You should have started earlier.

②ought to的用法：

to也表示“应该”，注意其肯定句、否定句、一般疑问句及回答。

You ought to obey the oughtn't to obey the law. Ought you to obey the

law----Yes，I ought to./No，I oughtn't to.

b.“ought to have done”表示（按规则）过去应做某事而实际未做．例如：

You ought to have helped him( but you didn’t).

这时，ought to与should可以互相换用．

注意，在美国英语中，ought to用于否定和疑问句时，to可以省略．例如: Ought you smoke so much You oughtn’t smoke so much．

③should与ought to的区别。

should侧重表示道德上理应如此，而ought to侧重表示在规则、条例或法律上应该如此。如：

You should go to class right away. According to the law you ought to obey the rules.

(六) will和would的用法

的用法：

①will表示请求、建议等。例如：

Will/Would you pass me the book

②表示意志、愿望和决心。例如：

I will never do that again．They asked as if we would do that again.

的用法：

①would是will的过去式。注意其两种固定问句的回答方式。

Would you like…----Yes，please./No，thanks.

Would you like to do…----Yes，I'd love to./I'd love to，but…./I'm sorry I can't.

②would与used to的区别：

would表示过去反复发生的动作，没有“现已无此习惯”的含义；而used to表示过去反复发生的动作或某种倾向，有“现已无此习惯”的含义。例如：He used to come here early，but now he doesn’t do it. He said he wou ld write many novels when he was young. He used to be a teacher，but now he isn’t.

3．will与would的区别：

would比will委婉客气；用“ will be”和“ will have done”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；而“would be”和would have done表示料想或猜想．例如：This will be the book you want．

He will have arrived by now.

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.

(七) ought to的用法

to也表示“应该”，注意其肯定句、否定句、一般疑问句及回答。

You ought to obey the oughtn't to obey the law. Ought you to obey the

law---Yes，I ought to./No，I oughtn't to.

2.“ought to have done”表示（按规则）过去应做某事而实际未做．例如：

You ought to have helped him( but you didn’t).

这时，ought to与should可以互相换用．

注意，在美国英语中，ought to用于否定和疑问句时，to可以省略．例如: Ought you smoke so much You oughtn’t smoke so much．

(八) used to的用法

used to表示过去的习惯动作或状态，现在已不存在（would do只能表示过去习惯性的动作而不能表示过去的状态，并且这种动作现在也可能存在），在间

接引语中，其形式可不变。注意在疑问句、否定句、否定疑问句或强调句中，可有两种式。例如

He told us he used to play football when he was young．

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：znt].

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

其反意疑问句或简略回答中，也有两种形式：

She used to be very fat，didn’t she/use(d) n’t she

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.

（九）had better与would rather的用法：

better 意为“最好”，后接不带to的不定式。例如:

-We had better go now.

-Yes，we had ( we'd better／we better had)

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：① had best与had better同意，但较少用。

② You had better …用于同辈或小辈，对长辈不可用．

rather意为“宁愿”，表选择，后接不带to的不定式。例如：

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, 因而后面可接than. 例如:

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)。

附：情态动词表示推测及“情态动词+have+done” 结构分析一、情态动词m u s t,c a n,c o u l d,m a y,m i g h t表推测的用法：

情态动词中的must, can, could, may, might都表推测。其中must的可能性最大，can / could次之，may / might最小。具体用法如下：

1.它们出现的句型不同：

must常用于肯定句中表推测，can常用于否定句和疑问句中表推测（也可以用于肯定句中，但不常见），could常用于肯定句、否定句和疑问句中表示推测；may/might常用于肯定句和否定句中表推测（might表推测时比may的可能性更小）。如：

He must be a can't be a teacher./Can he be a teacher The weather can be quite warm in winter. The plane could be delayed by fog. It couldn’t possibly be poison. He may/might be a may/might not be a teacher./Can he be a teacher You must have been to Shanghai. If you come here earlier yesterday，you could have met him. He can't/couldn't have been to the town. Can he have been to the town Where can (could) they have gone He may/might have finished the work. He may/might not have finished the work.

2.有两种不同的推测形式：

“can/could/may/might/must + be”表示对现在情况的推测，而“can/could，

may/might，must+ have done”则表示对过去的推测。must be为“肯定是，一定是”，can't/couldn't be为“不可能是”，may/might be为“可能是”，may/might not be为“可能不是”；must have done“肯定是做过……”，can/could not have done“不可能已经做过……”，may/mi ght have done“可能已经做过……”，may/might not have done“可能没有做过……”。例子见上面。

3.注意变反义疑问句：

如果它们后面接be，表示对现在的推测，变反义疑问句时，应将其当成be动词一般现在时态看待。如：He must be a teacher，isn't he He can't be a teacher，is he He may be a teacher，isn't he He may not be a teacher，is he

如果它们后面接have done，表示对过去的推测，变反义疑问句时：如果句中有了表示过去的具体的时间状语，应将句子当作实义动词的一般过去时态看待；如果句中没有具体的时间状语，应将句子当作现在完成时态看待。如：Lucy must have gone there yesterday，didn't she He must have finished his homework，hasn't he

下面这些短语不具有推测含义：could have done“本来能够做……而没有做”，ought to have done“本来应该做……而没有做”（表示从客观法律、义务或规则上看应该做……而没能做到），should have done“本来应该做……而没有做”（表示从主观上看应该做……而没能做到），needn't have done“本来不需要做……而已经做了”。如：We could have come here an hour earlier. You ought to have finished your homework. You needn't have come here early.

4.注意：

①must表示推测时很少用于将来的情况。一般不用He must come tomorrow.可用It’s certain / I’m sure that he will come tomorrow.

②may, might可以推测将来的情况。如：

I think we should take raincoat with us, it may rain.

我想我们应该带上雨衣，可能要下雨了。

She might not come this afternoon. 她今天下午可能不来了。

二、“情态动词+have+done” 结构的含义及用法

1、should have done/ should not have done

它们分别表示“过去本来应该（已经）…（而实际上并没有…）”/“过去本不应该（已经）…而实际上却已经…”如：

We should have studied last night, but we went to the concert instead . 我们昨晚本应学习的，但我们却去看音乐会了。（实际上没有学习）

If he had joined us , we should have had a more enjoyable time . 如果他加入我们

的活动，我们就可以玩得更开心了。（实际上没那么开心，由于他没加入我们的活动）

I should have thought of that .这一点我应该想到的。（但实际上没想到）

They shouldn't have left so soon . 他们不应当走得那么早。（但实际上还是走了）He shouldn't have said such a thing .他当时不应该说那种话。（但已经说了）

在表示推测时，它表示的是“大概已经，或许已经”的意思。如：

The train should have already left.火车大概已经开走了。

Time is up , you should have finished your exercises . 时间已到，你们可能已经做完作业了。

2、would have done

它表示的是与过去事实相反之假设的结果，意思是“当时就会…了”，而实际上没有……。如：

I would have helped you if I had known of your difficulties . 要是我当时知道你们的窘境，我就会帮助你了（而实际上没有帮助你）

If it hadn't rained yesterday, we would have gone on excursion .假如昨天没下雨，我们就去远足了。（实际上没有去）。

在表示推测时，它表示“过去大概是……，似乎、可能……”如：

I suppose the writer would have been about thirty when he published his first work . 我想这位作家出版第一部作品时，大概是30岁左右。

have done

它表示“过去一定……了”，且结果延续到现在，用于对过去发生的事进行推测。如：

No one answers the phone call, they must have already gene out ,没人接电话，他们一定已经出去了。

They must have arrived by now.现在他们想必已经到达。

You must have known what he wanted .你当时一定知道他要什么。

Where is my pen I must have lost it . 我的钢笔在哪我肯定把它弄去了。

have done/couldn't have done

这两个形式表示“过去应该不可能做…”如，

He can not have promised it . 他应该不会答应那种事。

John is very clever . He cannot have told his son to do that . 约翰是很聪明的，他应该不会叫他儿子那样做。

He couldn't have said such a thing . 他应该不会说出这样的事。

't have done

它表示"过去不可能做…"。如：

She can't have gone to school , we have no school today.她不可能到学校去，今天我们学校放假。

He can't have finished the work so soon .这项工作他不可能完成得这样快。

Jack doesn't work hard at all. He can't have passed this English examination . 杰克学习根本不用功。他不可能通过这次英语考试。

(c ould)…have done

这种形式只用于疑问句，表示"含疑问语气的推测"。如：

Where can (could) they have gone他们能到哪里去了呢

How could he have forgotten such an important thing这么重要的事他怎么能忘了呢

He told me he had a meeting to attend in Beijing. Can he have gone to Beijing to attend the meeting他告诉我说北京有个会议要参加，他会不会已位去了北京呢Can you have left the watch at home你会不会把表丢在家里呢

have done

它表示"过去本来能够…" 实际上没能做…。如：

I could have run 100 meters in 12 seconds.我本来能用12秒钟完100米的。（实际上设能）

If you could have finished the task in time，you could have been promoted. 如果你当时能如期完成那任务的话，你可能已提升了（实际上没有被提升）

I could have laughed to hear him talk like that.听他那样讲话，我差点笑出声来。

In those circumstances we could have held out longer.在那样情况下，我们本来可以坚持更久的。（实际上没有坚持很久）

(not) have done

它表示"对过去可能会(不会)发生的事" 的猜测。如：

She may have missed the train.她也许误了车。

He may not have achieved all his aims But his effort is a good one.他可能没达到他

的全部目的，但他还是认真做了努力的。

She may have gone to the clinic.她或许到医务宝去了。

"What has happened to Tom""I don’t know,. he may have got lost.""汤姆怎么了""

我不知道，他可能迷路了。

have done

a、它表示对过去发生的事一种不太肯定的猜测。如：

I thought my uncle might have missed the train..我想我叔叔可能误火车。

I might have lost my watch in the bath room.我可能把表遗忘在卫生间了。

b、它的虚拟式表示与过去事实相反的假设结果。如

If she had started a little earlier，she might have been in time for the train.如果她早点出发，她有可能及时赶上火车。(实际上没有早出发，便没有赶上火车)

It might have been better to stop them.如果那时就停上的话，也许比较好。

You might have told the truth.你本应该讲实话(实际上没有讲真话，此处有批评之意)

You might have made greater progress. 你的进步是可以更大一些的（此处含责备口气）

not have done

它表示过去已做的事，事实上没有必要。如：

I need not have got up so early . 我本来不必要那么早起床的（事实上早已起床）I need not have waited for the train for an hour. 我本来不必要等一个小时的火车。（事实上已经等了一个小时）