高中英语情态动词详细讲解及例句.doc

一、情态动词无人称和数的变化，不能单独做谓语，只能和行为动词或状态动词构成谓语
二、情态动词分为：情态助动词：can(could)、may(might)、must、have to (had to )、ought to 、
shall(should)、will(would) 12个
半情态助动词：dare、need、used to、had better、would better(5个)
三、情态助动词
1.can and could
1)ability：be able to do /manage to do/succeed in doing sth.
eg.The army can defeat their enemy.
eg.The army is able to defeat their enemy.
eg.The army succeed in defeating their enemy.
2)permission:eg.Can I smoke here?
eg.You can’t smoke here.
3)possibility:用在否定句、疑问句、感叹句中-
eg.This can’t be done by him.
当被用在肯定句中时，表达的是理论上的可能性，不涉及是否真的会发生
eg.even expert drives can make mistakes.
要表达现在或者将来的可能性，用may /might或could.
eg.I may leave for Beijing next month.
但在特殊疑问句中，或与副词hardly、only等连用的陈述句中表达可能
性只用can/could
Eg.where can the noise be coming from?
eg.It can hardly be the postman,he comes only in the morning.
4)有时会：the road can be blocked.
5)could 表示轻微的怀疑或委婉的看法
I’m sorry I couldn’t lend you the book now.
His story could be true,but I hardly think it is.
6)could 表示委婉的请求，主要用于疑问句，不用于肯定句
Could you lend me some money?
Yes,I can /No,I am afraid not.
7)could 的常用结构：could+动词+比较级 “非常，再.....不过了”
It couldn’t be better.
Couldn’t +过去分词+比较级“非常，再.....不过了”
They couldn’t have tried harder to make me eel welcome.
Can’t..too..=can never too“无论怎样...也不为过,越...越好”
I can’t thank you too much.I owe my progress to you.
Can’t (help/choose) but do/can but +动词原形“不得不，只好”
We can but agree with him.
Can’t help doing 忍不住，不得不
I can’t help laughing
Can’t be (it) 控制不住，没有办法
It can’t be helped
Can’t....without 没有...就不能
One can’t succeed without perseverance.

2. may and might
1) permission:May I use your pen?Yes,you may./No,you may not.
2) Possibility:用于推测，表示不确定,不用于疑问句中
She may know Tom’s address.
出现I’m afraid.I’m not sure等表示不确定时，常用may/might.
I’m afraid he might not come to attend the meeting today.
从语气上判断，may表示的可能性比might 大，might更多的表示怀疑
He may be very busy now.
He might be very busy now.
3)用于让步状语从句中
However hard you may study,you cannot master English in a month.
4) 用于祈使句，表示祝愿
May you succeed!
5)might 常用于表示轻微的责备和委婉的请求
You might post the letter for me if you are going near a post box.
You might have let me know before!
6) 习惯用法：may as well do”理所当然，有足够的理由”
She may be proud of her son
May /might (just) as well do=had better do(最好)
You might as well stay at home tonight.
May/might as well+do A+as+do+B”与其做B不如做A”
You might as well throw the money away as lend it to him.
One may as well not know a thing at all as know it but imperfectly
3. must and have to
1)表示义务，一定要，必须
You must arrive in good time.The meeting is very important.
2) 表示肯定性或难以避免，必然会，肯定会
All men must die.
3)must 表示有把握的推测，一定是，准时
Must do/must be doing/must have done
The tall fellow must be a basketball player.
Let’s have something.You must be starving.
He must have received mu letter which has mailed last week.
4) must 表示非要，偏要，常以第二人称为主语，意指不耐或令人不愉快的事情，用于其他 人称，表示主语固执，意为偏偏
Why must you buy that car?
Jane was never a pleasant young girl.After you gave her your advice,she must go
and do the opposite.
5）must 的三种否定形式
表示不可能 must be --can’t be must have done--can’t have done
You must have met him before.
You can’t have met him before.
表示不必 must do--need not to/don’t have to
We must get up at six tomorrow morning.
We don’t have to get up at six tomorrow morning.
表示决不能，严禁 must--mustn’t
You mustn’t park your car here.
6) 回答以must提问的句子
Must we clean all the rooms?
Yes ,you must/No ,you don’t have to/No ,you needn’t
7)must 可做名词，表示必须有的东西，必须做的事
Warm clothes are a must in the mountains.
8) must和have to 表示必须时，有一下差别
Must 表示的是说话人主观的看法，而have to则往往强调客观需要
The play is not interesting ,I really must go now.
I have to work when I was your age.
Must 一般只表现在，have to 则有更多的时态。
Had to/shall(will)have to/have had to/had had to
二者的否定意义大不相同，mustn’t表示禁止，不准 don’t have to 不必
且didn’t have to表示的是过去没有必要做，至于是否已做，要根据上下文判断。
You mustn’t go
You don’t have to
It was very kind of you to do the washing-up,but you didn’t have to do it

4. ought to 应该，表示义务或推测
1)肯定：主语+ought to do sth.
否定：主语+ought not to sth./oughtn’t to do sth.
疑问：ought +主语+to do sth.
2）表示推测时，与must 的区别，must比较肯定，直率。Ought to没那么肯定，比较含蓄
He must be home by now.
He ought to be home by now.
5. shall and should
1)shall用在疑问句第一和第三人称中,表示征求对方意见
What shall we do in the evening?
2)用在第二第三人称中，表示说话人的命令，警告或威胁
You shall fail if you don’t work harder.
He shall be punished.
3)在法律、条约、规章中，不论人称，一律用shall,表示义务、规定、预言等。
Each citizen shall carry his identification card when traveling.
Death is certain to all,all shall die.
4)表示劝告、建议、命令时，与ought to 同义
Should I open the window?
You should go to class right away.
You ought to go to class right away.
5)should 表示应该做时，有种道义上的责任
I should help him because he is in trouble.
6)should 还可以表示合理地推断，且所推断的几乎是事实，因此不是虚拟语气
Mary took dance lessons for years ,she should be an excellent dancer.
7)should 表示忧虑，惋惜等情绪时，有“竟会，竟然”的意思
You can’t imagine that a well-done gentleman should be so rude.
8)should 在疑问句中，常与how,why,who连用，表示不合理，难以相信
How should I know?
Why should him publish such a book?
6. will and would
1)will表示意愿，愿望，决心
I will never do that again.
2）表示推测，大概，想必=must/should/ought to指现在
It will be snowing in Beijing now.
3)表示习惯时多用于第三人称，意为通常，常常
He will sit here there hour after hour doing nothing.
4)will 表示自然规律
Oil and water will not mixed.
5)用于对一个讨厌的习惯和无生命体进行批评
Jack will leave the lights on when he’s last out of the office
Whatever I do,my car won’t start first time on the cold morning.
6)用在if条件句中
表示意志，意为insist on
If you will go out without a coat ,you will catch a cold.
表示有礼貌的劝阻，意为be willing to
If won’t stop smoking,you can only except to have a bad cough.
表示对将来行为的预测
If he won’t arrive before ten,there’s no point in ordering meal for him.
7)would 可以表示过去反复发生的动作或某种倾向，与used to 不同没有“现在已无此习惯” 的含义 During the vacation he would visit me every week.
8)would 表示估计和猜想
It would be ten when he left home.
9）would 表示谦恭的请求，常用于疑问句
Would you tell me the way to the station.
10)won’t 和would not 常用于表示“坚决地拒绝”
He would not let me enter the room.
半情态助词
1. dare 和need 的用法
1）二者做情态动词时，主要用于疑问句、否定句和条件从句，dare既可指现在，也可指去
He daren’t speak English before such a crowd ,dare he?
The president was so hot-tempered that no one dare tell him the bad news.
You needn’t come so early
2)need 在做情态动词时，引起的问句的回答方式
Need I finish the work today?
Yes,you must/have to /ought to /should
No, you needn’t/don’t have to
3)二者做实义动词时，有人称时态数的变化
Dare to do sth.
Not dare(to)do sth.eg.he does not dare (to)answer.
Need to do sth现在
Didn’t need to do sth.过去
Will need将来
4）didn’t need to do 和needn’t have done前者不必做某事，后者本不必做但实际上已经做了
We didn’t need to take warm sweaters,as the weather was so good.
We needn’t have taken warm sweaters.We could have used the space in our luggage for more books!
5)与dare 构成的一些惯用语
How dare+句子，表示“竟敢”
How dare you open my drawer without my permission?
I dare say “我以为，我想”
He is not here yet,but I dare say he will come latter
Don’t you dare用于警告他人不许做某事“你敢”
Don’t you dare come here again!
2. used to /had better to /would rather 的用法
1）used to 只有过去形式，不用于现在将来，表曾经有某种习惯
He told us he used to play football when he was young
在疑问句中Did you use to go there to see your brother?
Used you to go there to see your brother?
Yes ,I did/I used to

No ,I didn’t/I usedn’t
在否定句中I didn’t used to go there.
I usedn’t to go there.
在强调句中 I used to smoke ,but it was a long time ago.
I did use to smoke,but it was a long time ago.

在反意疑问句中 she used to be very fat,didn’t she /usedn’t she?
2)had better/best do 没有词形的变化,主义you had better 不能用于对长辈
We had better go now
3）would rather ，没有词形的变化，接原形表示现在或将来如表示过去的意愿可接完成时
I’d rather not have told her the news.
Would rather do ....than do...
I would rather lose a dozen cherry trees than know that you have told
me one lie
情态动词+完成式
1）could have done用于谈论过去的情况，肯定句中表示那时可能，否定句中表示怀疑，
用于虚拟语气表示某事过去可能发生而实际位发生，意为“本可以”
John could have posted the letter.
She couldn’t have done it ;she is such a nice girl
The accident could have been prevented.
注意 can have done 仅用于否定句和疑问句，表示从现在的眼光看过去
而could have done 还可以表示从过去的某个时间段看之前发生的事情
Can she have got the book?
He asked to see his exam paper,feeling sure that he couldn’t have made
such a mistake.

2) may /might have done表示对过去发生行为的推测，might have done 含有批评,责备，忠告的意味
He may have finished the exercise ,but he didn’t hand in.
She might have gone off with some new friends,leaving us alone
You might have told me about the party.
3)must have done 常用在肯定句中，表示对过去发生的行为的逻辑推测“一定，想必”它的否定形
式是can’t/couldn’t have done
You must have read the book.
4) needn’t have done 过去做了本不必做的事情
You needn’t have watered the flowers,for it is going to rain.
5) should have done本该做而实际上没做，其否定形式表示本不该发生却发生了
You should have stared earlier,but you didn’t
She shouldn’t have taken away my book,for I wanted to use it
6) will have done表示说话人确信某事已经发生，但不确知，常用于二三人称，否定为won’t have done

We sent the invitations on Monday,so they will have received by now.
Why hasn’t anyone replied?
7) ought have done过去应该做而实际没有做，与should 常换着用，也常用于对过去不当行为的指责
You ought to have helped him.
You ought to have told me about it earlier.