情态助动词
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现在时形式/过去时形式
Can/could may/might will/would shall/should must need dare/dared ought to used to
一、表示“能力”和“可能”
1、表示能力,可用can, could, be able to。
Can 既能表示现在的能力,也能表示将来的
能力。
I can’t do it now, but I can do it later.
Can泛指一般能力时,可以与be able to 交替使用。
2、表示“可能”,可用may, might, can, could.
可能性:might <may<could <can
3、疑问句中表示“可能”,须用can而不用may,“不可能”用can’t 表示
Can表示可能,常用于疑问句和否定句中
二、表示“许可”或“不许”
1、请求对方的“许可”,可用can, could, may, might。
Could, might 比较委婉,更有礼
貌。
Could I use your car? ----- Yes, of course you can.
Could I use your car? ----- No, you can’t
2、其他委婉的拒绝:
Could I go out for a moment? ----- No, I’m afraid not.
三、表示“义务”“必然”
1、表示“必须”、“应该”做某事,可用should, ought to, must。
should/ ought to 表示“劝说”“敦促”含义
Should/ ought to +不定式完成体,表示“本应该做的却没有做”
2、Must 表示强烈的劝说或敦促时,说话者是权威一方。
You must be back by ten o’clock.
表示将来的“必须”,常用(will/ shall) have to。
过去则用had to
You must do it again. (表示现在)
I really must stop smoking. (表示将来)
I had to leave at six yesterday. (表示过去)
3、must的否定形式must not / mustn’t 表示“不许”“禁止”
You mustn’t/ are not to talk like that. 过去时: You weren’t to talk like that.
Must you leave so soon? No. I needn’t
Must 与have to的区别:must侧重主观,have to 侧重客观
四、表示“预见”和“推测”
1、表示推测除了should, ought to和must外, will/ would也用于将来或一般时态的推测
I will be a different person when I live in England.
五、表示“意愿”“意图”“决心”
1、表示意愿,可以用will, would, shall
You can help me if you will.
Will/ would you please open the door? ——yes, I will.
2、shall 表示意愿,适用于第二、三人称作主语
You shall stay with us as long as you like.
3、第一人称主语表示意图和决心,用shall表示征求对方意见。
I shall never do that again.
Shall we go?
4、will 表示决心或坚持要做某事。
I will take the job and no one is going to stop me.
六、其他情态含义
1、should 在某些语境中表示惋惜、忧虑、欢欣、惊讶等等。
例如某些that从句
It’s a pity that he should leave so soon.
It’s unbelievable that he should be working so hard.
惯用的疑问句和感叹句:
How should I know?
Why should he be resigning?
That he should dare to attack me!
Who should come in but the mayor himself?
3、表示“胆敢”,dare用于否定句和疑问句。
daren’t 否定形式
He dare not go there.
Tom wanted to come, but he daren’t.
4、need 情态助动词,表示“必须”“需要”,用于否定句和疑问句中
He needn’t worry about it. /Deed I collect the parcel myself?
Need we work late today? No, you needn’t.
Must I see a doctor at once? No, you needn’t.
5、used to 表示过去习惯动作或状态
he used to smoke a lot, but he has long given up smoking.
七、情态助动词的推测性用法
不确定might May Could Can Should Ought to Would Will Must 确定That might be George. That must be George.
能做推测的情态助动词的句法特征
1、后面可加完成体形式
You must have been disappointed. You can’t have been disappointed.
2、后面可加进行体
He must be working late at the office.
3、可用于there be 存在句
There must be some mistake.
4、后面为一般形式时,通常是静态动词
He must be there. He must understand that we mean business.
5、主语可以是无生命物的名词
It must be George.。