第1个回答 2014-01-03
1 情态动词的语法特征
1) 情态动词不能表示正在发生或已经发生的事情,只表示期待或估计某事的发生。
2) 情态动词 除ought 和have 外,后面只能接不带to 的不定式。
3) 情态动词没有人称,数的变化,即情态动词第三人称单数不加-s。
4) 情态动词没有非谓语形式,即没有不定式,分词,等形式。
2 比较can 和be able to
1)can could 表示能力;可能 (过去时用could),
只用于现在式和过去式(could)。be able to可以用于各种时态。
They will be able to tell you the news soon. 他很快就能告诉你消息了。
2)只用be able to
a. 位于助动词后。
b. 情态动词后。
c. 表示过去某时刻动作时。
d. 用于句首表示条件。
e. 表示成功地做了某事时,只能用was/were able to, 不能用could。
He was able to flee Europe before the war broke out.
= He managed to flee Europe before the war broke out.
注意:could不表示时态
1)提出委婉的请求,(注意在回答中不可用could)。
--- Could I have the television on?
--- Yes, you can. / No, you can't.
2)在否定,疑问句中表示推测或怀疑。
He couldn't be a bad man.
他不大可能是坏人。
3 比较may和might
1) 表示允许或请求;表示没有把握的推测;may 放在句首,表示祝愿。
May God bless you!
He might be at home.
注意: might 表示推测时,不表示时态。只是可能性比may 小。
2) 成语: may/might as well,后面接不带to 的不定式,意为"不妨"。
If that is the case, we may as well try.
典型例题
Peter ___come with us tonight, but he isn't very sure yet.
A. must B. may C. can D. will
答案B. 表可能性只能用may. 此句意可从后半句推出。
4 比较have to和must
1) 两词都是'必须'的意思,have to 表示客观的需要, must 表示说话人主观上的看法,既主观上的必要。
My brother was very ill, so I had to call the doctor in the middle of the night. 我弟弟病得很厉害,我只得半夜里把医生请来。(客观上需要做这件事)
He said that they must work hard. 他说他们必须努力工作。(主观上要做这件事)
2) have to有人称、数、时态的变化,而must只有一种形式。但must 可用于间接引语中表示过去的必要或义务。
He had to look after his sister yesterday.
3) 在否定结构中: don't have to 表示"不必"
mustn't 表示"禁止",
You don't have to tell him about it. 你不一定要把此事告诉他。
You mustn't tell him about it. 你一定不要把这件事告诉他。
5 must表示推测
1) must用在肯定句中表示较有把握的推测,意为"一定"。
2) must表对现在的状态或现在正发生的事情的推测时, must 后面通常接系动词be 的原形或行为动词的进行式。
You have worked hard all day. You must be tired. 你辛苦干一整天,一定累了。(对现在情况的推测判断)
He must be working in his office. 他一定在办公室工作呢。
比较:
He must be staying there.
他现在肯定呆在那里。
He must stay there.
他必须呆在那。
3) must 表示对已发生的事情的推测时,must 要接完成式。
I didn't hear the phone. I must have been asleep. 我刚才没有听到电话,我想必是睡着了。
4) must表示对过去某时正发生的事情的推测,must 后面要接不定式的完成进行式。
---Why didn't you answer my phone call?
---Well, I must have been sleeping, so I didn't hear it.
5) 否定推测用can't。
If Tom didn't leave here until five o'clock, he can't be home yet. 如果汤姆五点才离开这儿,他此时一定还未到家。
第2个回答 2006-02-23
情态动词是一种本身有一定的词义,表示说话人的情绪,态度或语气的动词,但不能单独作谓语, 只能和其他动词原形构成谓语。
We can be there on time tomorrow.我们明天能按时去那儿。
May I have your name? 我能知道你的名字吗?
Shall we begin now?我们现在就开始吗?
You must obey the school rules.你必须遵守校规。
情态动词数量不多,但用途广泛,主要有下列:
can (could), may (might), must, need, ought to, dare (dared), shall (should), will (would) .
情态动词的位置:
情态动词在句中放在谓语动词之前, 谓语动词前若有助动词,则在助动词之前,疑问句中, 情态动词则在主语之前。
I can see you. Come here. 我能看见你,过来吧。
He must have been away.他一定走了。
What can I do for you?你要什么?
How dare you treat us like that!你怎能那样对待我们!
情态动词的特点:
情态动词无人称和数的变化, 情态动词后面跟的动词需用原形,否定式构成是在情态动词后面加 "not"。 个别情态动词有现在式和过去式两种形式, 过去式用来表达更加客气, 委婉的语气, 时态性不强, 可用于过去,现在或将来。
He could be here soon.他很快就来。
We can't carry the heavy box.我们搬不动那箱子。
I'm sorry I can't help you.对不起,我帮不上你。
情态动词的用法:
can (could) 表示说话人能,可以,同意,准许,以及
客观条件许可,could 为 can 的过去式。
Can you pass me the books? 你能给我递一下书吗 ?
Could you help me, please? 请问,你能帮助我吗?
What can you do? 你能干点什么呢?
Can you be sure?你有把握吗?
can 和could 只能用于现在式和过去式两种时态,将来时态用 be able to 来表示。
He could help us at all.他完全可以帮助我们。
With the teacher's help,I shall be able to speak English correctly.由于老师的帮助,我将能准确地讲英语。
may (might) 可以, 表示说话人同意,许可或请求对方许可。
You may take the book home. 你可以把书带回家去.
May I come in? 我可以进来吗?
may 否定式为 may not, 缩写形式是 mayn't.
might 是may 的过去式, 有两种用法, 一种表示过去式,一种表示虚拟语气, 使语气更加委婉, 客气或对可能性的怀疑。
He told me he might be here on time.
他说他能按时间来。
Might I borrow some money now.
我可以借点钱吗?
Must 必须,应该,一定,准是, 表示说话人认为有必要做某事, 命令, 要求别人做某事以及对事物的推测。
must 用来指一般现在时和一般将来时, 过去式可用 have to 的过去式代替。
I must finish my work today.
我今天必须完成我的工作。
You mustn't work all the time.
你不能老是工作。
must + have + 过去分词,表示现在对过去事物的推测。
He must have told my parents about it.
他一定把这件事情告诉我父母亲了。
He must have received my letter now.
他现在一定收到我的信了。
It's six o'clock already, we must have been late again.
已经六点钟了,我们一定又迟到了。
must 和 have to 的区别: must 表示说话人的主观思想, have to 表示客观需要。
You must do it now.
你必需现在就干。(说话人认为必须现在干)
I have to go now.
我得走了。(客观条件必须现在走)
need 需要 多用在否定式或疑问句中.
need 是一个情态动词, 他的用法完全和其他情态动词一样, 但 need 还可当作实义动词使用, 这时 need 就象其他动词一样,有第三人称,单复数, 后面加带 to 的动词等特性。
I need a bike to go to school.
我上学需要一辆自行车。
needn't + have + 过去分词 表示过去做了没必要做的事情。
You needn't have taken it seriously.
这件事情你不必太认真。
dare 敢 多用在否定或疑问句中。
The little girl dare not speak in public.
小女孩不敢在公众面前说话。
Dare you catch the little cat?
你敢抓小猫吗?
dare 除用作情态动词外,更多的是当实义动词使用, 用法同实义动词一样,要考虑人称,单复数,时态等。
ought 应当,应该 后面跟带有 to 的动词不定式。
You ought to read these books if you want to know how to repair the motorcar.
如果你想知道如何修理汽车,你应该读这些书。
You ought to bring the child here.
你应该把孩子带来。
ought + to have done 句型。指过去动作,表示一件事情该做而未做。
You ought to have been here yesterday.
你昨天就应该来。
ought not to have done 句型。表示一件不该做的事情却做了。
You ought not to have taken the book out of the reading-room.
你不应该把书带出阅览室。
will (would)决心,愿望。 would 为 will 的过去式,
可用于各人称。
I'll do my best to catch up with them.
我要尽全力赶上他们。
I'll never do it again, that's the last time.
我再不会做那件事情了,这是最后一次。
He said he would help me.
他说他会帮助我。
will, would用于疑问句表示说话人向对方提出请求或询问,用 would 比 will 更婉转,客气。
It's hot. Will you open the windows?
天气太热了,你能打开窗户吗?
Will you help me to work it out?
你能帮我解这道题吗?
Would you like some coffee?
给你来点咖啡怎样?
Shall, should表示命令,警告,允诺,征求,劝告,建议惊奇。
You should hand in the exercise book.
你应该交作业本儿了。
This should be no problem.
这应该没问题。
Shall we go now.
我们现在可以走了吗?
Why should I meet him?
为什么我要见他?
have to,不得不,必须,表示客观条件只能如此, 而must 则表示主观思想必须。
I have to go now.
我现在得走了。
I have to cook for my child.
我得给孩子做饭。
You must be here on time next time.
你下次一定要按时来。
We must go to get the timetable ourselves.
我们一定要自己去拿时刻表。
第3个回答 2006-02-23
情态动词的定义:
情态动词是一种本身有一定的词义,表示说话人的情绪,态度或语气的动词,但不能单独作谓语, 只能和其他动词原形构成谓语。
We can be there on time tomorrow.
我们明天能按时去那儿。
May I have your name?
我能知道你的名字吗?
Shall we begin now?
我们现在就开始吗?
You must obey the school rules.
你必须遵守校规。
情态动词数量不多,但用途广泛,主要有下列:
can (could), may (might), must, need, ought to, dare (dared), shall (should), will (would) .
情态动词的位置:
情态动词在句中放在谓语动词之前, 谓语动词前若有助动词,则在助动词之前,疑问句中, 情态动词则在主语之前。
I can see you. Come here.
我能看见你,过来吧。
He must have been away.
他一定走了。
What can I do for you?
你要什么?
How dare you treat us like that!
你怎能那样对待我们!
情态动词的特点:
情态动词无人称和数的变化, 情态动词后面跟的动词需用原形,否定式构成是在情态动词后面加 "not"。 个别情态动词有现在式和过去式两种形式, 过去式用来表达更加客气, 委婉的语气, 时态性不强, 可用于过去,现在或将来。
He could be here soon.
他很快就来。
We can't carry the heavy box.
我们搬不动那箱子。
I'm sorry I can't help you.
对不起,我帮不上你。
情态动词的用法:
can (could) 表示说话人能,可以,同意,准许,以及
客观条件许可,could 为 can 的过去式。
Can you pass me the books?
你能给我递一下书吗 ?
Could you help me, please?
请问,你能帮助我吗?
What can you do?
你能干点什么呢?
Can you be sure?
你有把握吗?
can 和could 只能用于现在式和过去式两种时态,将来时态用 be able to 来表示。
He could help us at all.
他完全可以帮助我们。
With the teacher's help,I shall be able to speak English correctly.
由于老师的帮助,我将能准确地讲英语。
may (might) 可以, 表示说话人同意,许可或请求对方许可。
You may take the book home.
你可以把书带回家去.
May I come in?
我可以进来吗?
May I use your dictionary?
我可以用你的词典吗?
You may put on more clothes.
你可以多穿点衣服.
He said he might lend us some money.
他说他可以借给我们一些钱。
may 否定式为 may not, 缩写形式是 mayn't.
might 是may 的过去式, 有两种用法, 一种表示过去式,一种表示虚拟语气, 使语气更加委婉, 客气或对可能性的怀疑。
He told me he might be here on time.
他说他能按时间来。
Might I borrow some money now.
我可以借点钱吗?
He might be alive.
他可能还活着。
Must 必须,应该,一定,准是, 表示说话人认为有必要做某事, 命令, 要求别人做某事以及对事物的推测。
must 用来指一般现在时和一般将来时, 过去式可用 have to 的过去式代替。
I must finish my work today.
我今天必须完成我的工作。
You mustn't work all the time.
你不能老是工作。
Must I return the book tomorrow?
我必须明天还书吗?
After such a long walk, you must be tired.
走了这么长的路,你一定困了。
He must be the man I am looking for.
他一定是我要找的人。
He had to go because of somebody's calling
him that day.
那天他要走是因为有人叫他。
must + have + 过去分词,表示现在对过去事物的推测。
He must have told my parents about it.
他一定把这件事情告诉我父母亲了。
He must have received my letter now.
他现在一定收到我的信了。
It's six o'clock already, we must have been late again.
已经六点钟了,我们一定又迟到了。
must 和 have to 的区别: must 表示说话人的主观思想, have to 表示客观需要。
You must do it now.
你必需现在就干。(说话人认为必须现在干)
I have to go now.
我得走了。(客观条件必须现在走)
need 需要 多用在否定式或疑问句中.
Need I attend the meeting tomorrow?
我需要明天参加会议吗?
You need not hand in the paper this week.
这一周你不必交论文。
need 是一个情态动词, 他的用法完全和其他情态动词一样, 但 need 还可当作实义动词使用, 这时 need 就象其他动词一样,有第三人称,单复数, 后面加带 to 的动词等特性。
I need a bike to go to school.
我上学需要一辆自行车。
Do you need a dictionary?
你需要词典吗?
She needs a necklace.
她需要一条项链。
needn't + have + 过去分词 表示过去做了没必要做的事情。
You needn't have taken it seriously.
这件事情你不必太认真。
dare 敢 多用在否定或疑问句中。
The little girl dare not speak in public.
小女孩不敢在公众面前说话。
Dare you catch the little cat?
你敢抓小猫吗?
dare 除用作情态动词外,更多的是当实义动词使用, 用法同实义动词一样,要考虑人称,单复数,时态等。
Do you dare to walk in the dark?
你敢黑夜走路吗?
He doesn't dare to tell the teacher what happened that day.
他不敢告诉老师那天发生的事。
ought 应当,应该 后面跟带有 to 的动词不定式。
You ought to read these books if you want to know how to repair the motorcar.
如果你想知道如何修理汽车,你应该读这些书。
You ought to bring the child here.
你应该把孩子带来。
ought + to have done 句型。指过去动作,表示一件事情该做而未做。
You ought to have been here yesterday.
你昨天就应该来。
ought not to have done 句型。表示一件不该做的事情却做了。
You ought not to have taken the book out of the reading-room.
你不应该把书带出阅览室。
will (would)决心,愿望。 would 为 will 的过去式,
可用于各人称。
I'll do my best to catch up with them.
我要尽全力赶上他们。
I'll never do it again, that's the last time.
我再不会做那件事情了,这是最后一次。
He said he would help me.
他说他会帮助我。
will, would用于疑问句表示说话人向对方提出请求或询问,用 would 比 will 更婉转,客气。
It's hot. Will you open the windows?
天气太热了,你能打开窗户吗?
Will you help me to work it out?
你能帮我解这道题吗?
Would you like some coffee?
给你来点咖啡怎样?
Shall, should表示命令,警告,允诺,征求,劝告,建议惊奇。
You should hand in the exercise book.
你应该交作业本儿了。
This should be no problem.
这应该没问题。
Shall we go now.
我们现在可以走了吗?
Why should I meet him?
为什么我要见他?
have to,不得不,必须,表示客观条件只能如此, 而must 则表示主观思想必须。
I have to go now.
我现在得走了。
I have to cook for my child.
我得给孩子做饭。
You must be here on time next time.
你下次一定要按时来。
We must go to get the timetable ourselves.
我们一定要自己去拿时刻表。