[英语语法手册]情态动词--can, could

2012-08-02 14:48:49 英语

助动词

be的形式变化和动词bebe作为助动词的用法有下列几种:

1)be后跟动词的现在分词 可以构成各种进行时态。如:

The driver is cleaning the car.司机在擦车。

Yesterday afternoon we were discussing a new plan.昨天下午我们在讨论一个新的计划。

Women in our country are playing an important part in socialist construction.我国妇女在社会主义建设中正起着重要的作用。

2) be后跟动词的过去分词 可以构成被动语态。如:

A lot of consumer goods are made of nylon.许多消费品都是尼龙作的。

The Flower Show is usually held here in October. 花展通常于10月在此举行。

The cinema will be closed for repair from March 3rd.影院自三月三日起修理内部停止营业。

3)be加动词不定式 有下列各种用法:

a)表示未来的安排或计划。如:

The delegation is to leave for Shanghai tomorrow.代表团定于明天去上海。

I'm to be home before midnight.我午夜前一定回来。

b)表示必要或命令或问对方的意志。如:

You're to hand in your exercises tomorrow.你们明天要交练习。

Where am I to put these tools? 这些工具应该放在什么地方?

What is to be done?怎么办?

c)表示"可能",与canmay相仿。如:

I am not sure whether he is to turn up tonight.我不能断定他今晚是否能来。

My key is nowhere to be found.我哪儿也找不着我的钥匙。

d) be + about + 动词不定式则表计划即将,如:

The meeting is about to begin.会议即将开始。

have

的过去式是hadHave (had)作为助动词和过去分词一起,构成各种完成时态。如:

I have known Mr. Smith for four years.我认识史密斯先生已经四年了。

He has not made up his mind yet.他还没有决定呢。

A woman came in with a babywho had just swallowed a safety pin.一个妇女带进来一个刚吞进一个别针的婴儿。

[] have的简略式是'vehas的简略式是'shad的简略式是'd,如

I'veyou'vehe'sI'dwe'dhe'dthey'd等。

do

的过去式是diddo (did)作为助动词,有下列一些用法:

1)构成现在一般时和过去一般时的疑问句和否定句。如:

Do you know each other? 你们两人认识吗?

How do you find the climate here? 你觉得这里的气候怎么样?

She did not go to hospital after breakfast She went to work as usual.早饭后她没有去医院,她照常上班去了。

2)构成否定的祈使句。如:

Don't be so careless.不要那么粗枝大叶。

Do not hesitate to come when you need help.有困难只管来。

3)加强陈述句和祈使句的语气。如:

I do think he is right.我确实认为他是对的。

Do come often.一定常来呀。

Do askif you have any questions.如果有问题,务必提出。

4)用于倒装句中。如:

Only then did I understand the importance of science.只是到了那时,我才了解到科学的重要性。

Never did I expect to see him there.我从未想到会在那里看到他。

5)还可用来代替主要动词,以避免重复。较常用在简略答语中。如:

Does he also study geography?他也学地理吗? ――Yeshe does.是的,他也学地理。

Did it snow a lot last week? ――Yesit did。上星期雪下得多吗? --是的,下得很多。

He works even harder than you do. 他比你还要用功。

[] 上面最后一句中的do应唤作替代词,只是为了初学者的方便而放在助动词项下。

shallWill

助动词

shall本身没有词义,只用在第一人称的将来时态中(现多为will所代替)。在将来一般时中,shall后接动词原形。如:

I shall think it over.我要好好考虑一下。

Don't worry. We shall tell you all about it.你别担心。我们都会告诉你的。

助动词

will本身没有词义,只用在第二、三人称的将来时态中。will在将来一般时中后接动词原形。如:

He will be twenty-five years old next month.他下个月将是二十五岁。

You will have an examination in English tomorrow.你们明天有英语考试。

The weather forecast says that there'll be heavy rain tomorrow.天气预报明天有大雨。

shouldwould

助动词

shouldshall的过去式,它本身没有词义,用于第一人称的过去将来时态中(现多用would)should在过去将来一般时中后接动词原形。如:

We were told that we should sight the Treasure lsland that night. 我们被告知那天夜里我们就要看见宝岛了。

助动词

wouldwill的过去式,它本身没有词义,用于第二、三人称的过去将来时态中。would在过去将来一般时中后接动词原形。如:

He said that he would always remember that day.他说他将永远记住那一天。

[英语语法手册]情态动词概述

特征

1)情态动词(modal verb)本身有词义,表示说话人的语气或情态,但词义不完全,不能单独用作谓语动词,一般只能和动词原形一起构成谓语动词。

2)情态动词所表示的情态有:命令、允诺、请求、拒绝、愿望、愿意、义务、必要、可能、能力、敢于、需要等。

3)情态动词(ought除外)和助动词shallwillshouldwould一样,后面的动词不定式一般皆不带。

形式变化

1)没有人称和数的变化,第三人称单数的现在时也无变化。如:

I can We can

You can You can

He

They can

She can

It

2)有些情态动词有过去式,有少数过去式和它的原形相同。

a)有过去式的情态动词有:

may -- would

can ―― could

may―― night

shall -- should

have to -- had to

b)过去式不变的情态动词有:

must - must (had to)

ought to - ought to

need---need

dare - dare(亦可用dared)

3)大多数情态动词后面可用动词的进行式、完成式和被动形式,如:can(maymust)be doingcan(maymust) have donecan(maymust)be done等。

否定式

情态动词和助动词一样,后面可直接跟否定词not。现将情态动词的否定式及其否定式的简略式(简略式用于口语中)列举如下:

shall not--shan't [FB:nt]

will not---won't [wEunt]

can not-can't [kB:nt]

must not-mustn't [5mQsnt]

should not-- shouldn't

would not-- wouldn't

could not-- couldn't

dare not- daren't [dZEnt]

need not-- needn't

在疑问句中的用法

情态动词在疑问句中的用法和助动词相同。如:

May I ask you a question? 我可以问你一个问题吗?

Can you let me use your dictionary for a minute? 你能把字典借我用一会儿吗?

Would you like to visit the heavy machinery plant? 你想参观重型机器厂吗?

注意have to在疑问句中的位置。如:

Do you have to go out today? 你今天一定得出去吗?

Does he have to finish the work tomorrow? 他明天非做完这项工作不可吗?

 

cancould

can的词义

表示体力或脑力方面的"能力"或客观上的"可能"。如:

Can you ride a bike? YesI can.你能骑自行车吗?是的,我能骑。

Can Mr. Smith use chopsticks? Nohe can't . 史密斯先生会用筷子吗?不,他不会。

Most women here can read and write now.这里的多数妇女都能识字,也会写字。

In China even barren mountains can be turned into fertile fields. 在中国,荒山也能变成良田。

can用在否定句和疑问句中时

在这种句子中,can常可意谓"可能",表示猜测和推理。如:

It surely can't be six o'clock already? 不可能已经六点钟了吧?

You can't be hungry so soonTom. You've just had lunch. 顿姆,你不可能饿得这么快,你刚吃过午饭。

She cannot be so careless. 她不可能这么粗心。

Where can he be? 他会在什么地方呢?

What can he mean? 他会是什么意思呢?

It surely can't be six o'clock already? 不可能已经是六点钟了吧?

[注一] can加动词的进行时态,也可表示"可能"。如:

What can he be doing all this time? 他一直会是在干什么呢?

She cannot be playing ping-pong now.她现在不可能在打乒乓球。

[注二] 在日常会话中,can可代替may表示"允许"may比较正式,如:

You can drop in any time. 你随时都可以来串门。

Can I use your basin? of courseyou can.我可以用你的脸盆吗?--当然可以。

You can have my seatI'm going now.我要走了,你坐我的座位吧。

Could

couldCall的过去式,表示与过去有关的1)能力和2)可能(在否定和疑问句中)。如:

1)We were sure that he could do the work. 我们肯定他能做这工作。

He was a farmhand. He could not afford to send his son to school. 他是个雇农,他供不起儿子上学。

2)At that time we thought the Story could not be true.那时我们以为所说的事不可能是真的。

[] could可代替can表示现在,但语气较为婉转。如:

could you wait half an hour?请你等半个小时好吗?

could you please ring up again at six? 六点钟请你再来电话好吗?

could we visit a kindergarten? I've been wanting to see one ever since I came to China.我们可以访问一个幼儿园吗?我自从到中国来以后,一直想看一所幼儿园。

[注二]表示过去的能力并已完成一具体动作时须用were (was) able (to),不可用could。如:

I am glad we were able to catch the train. 我很高兴我们能赶上火车。但如未完成一具体动作,则可用could not。如:

I am sorry we couldn't (weren't able to) catch the train.我很遗憾我们没有能赶上火车。

can的形式

can只有现在式can和过去式could两种形式,能表示现在一般和过去一般两种时态,有时也能表示将来。所有其他时态(包括将来)须用be able加动词不定式来表示。如:

With their help, we shall be able to finish the work in a few days. 有他们的协助,我们将会在几天之内完成这项工作。

They have not been able to come to Boston. 他们没有能到波斯顿来。

Mr. Johnson rang up just now to Say that he won't be able to come over this evening.约翰逊先生刚来电话,说今天晚上他来不了。

cancould用于否定或疑问句中

can (could)用于否定或疑问句中后面跟动词原形的完成式时,表示对过去发生事件的"可能性"。而couldcan更加表示说话人的"不肯定的"语气。如:

Can he have left already? 他会是走了吗?

Could she have forgotten my address? 她会把我的地址忘记了吗?

It couldn't have been henry. He has gone to the factory. 不可能是亨利,他已经去工厂了。

Surely she can not have arrived so early. 他当然不可能这么早到这里的。

[] could加动词的完成式时,有时表示"过去可能完成但事实上并没有实现的动作"。如:

You could have done the work better.你本来可以做得更好些。(事实上你做得不那么好)

You could have got the early train.你本来可以搭上早班火车的。(事实上没搭上)

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