情态动词用法及区别.doc
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情态动词用法及区别一、情态动词can、could、may
情态动词是表示说话人的某种感情或语气的动词,用来表示请求、允诺、愿望、建议、命令、能力、需求或拒绝等情感态度,常用的情态动词有:can、could、may、might、need、dare、ought to、will、would、shall、should等情态动词can表示现在的能力,could 表示过去的某种能力,如:
He can speak good English
Sandy cannot dance
The old man could swim across the river when he was young
注意:我们可以用be able to 来表示能力,be 动词的形式根据句子所用时态变化
我们可以用情态动词may、could、can来表示许可情态动词could 表示一种委婉的语气,比用can 更有礼貌,may较正式。如:
Can I use your pen?
Could we picnic here?
May I see the letter?
拓展:1、情态动词的用法:情态动词有一定的词义,但不能单独做谓语,必须与实义动词或连系动词连用,构成谓语。如:
Can I have a look at your photo?
You may take whatever you like
情态动词一般无人称和数的变化,如:
We must stay in the classroom
He must give up smoking
有些情态动词有现在式和过去式两种形式,如:
may can must ought to will shall need dare 过去式 might could — — would should — dared 有些过去式不代表过去。如:
You might be right
I would like to have a talk with you
情态动词后接动词原形,即不带to的不定式。如:
She may lose her way
情态动词具有助动词的作用,可用来构成否定句、疑问句及用于简略回答。如:
Can you sing English songs?
Yes ,I can
常用情态动词的用法:May的用法:
表示允许或征询对方许可,有“可以”的意思。May not 表示说话人“不许可”。如:
You may go now
May I use your computer?
You may not go=I do not permit you to go
在回答may引导的疑问句时,肯定回答:yes,you may,否定:no,you can’t或no,you’d better not。在表示“不可以,禁止,阻止”的意思时,常用must not/mustn’t,如:
——May I come in?
——yes,please
——may I smoke here?
——yes,you mayno,you mustn’t
may 表示可能,通常只用于陈述句。May所表示的可能性比might大。如:
You may be right
It might rain this afternoon
在口语中,can 可代替may 表示许可,而may比较正式。如:
Class is over,you can go home now
Can I use your camera?
might,could 用于现在时,语气较为委婉、礼貌,如:
Might/could I invite you to dinner?
Can 的用法:
表示能力,有“能,会,能够”的意思,如:
——can you drive a car?
——yes, can/no, can’t
表示可能性,常用于否定句或疑问句,如:
Can it be true?
Today is Sunday ,he can’t be at school
can 和be able to的用法比较
两者可以互换,但can用来表示能力时,只有过去时和现在式两种,其他时态要用be able to
中考热点:
Can 与 be able to不通用的情况:
如果我们要表示一个动作成功的完成了,那么必须使用was able to,而不能用could,如:
He didn’t agree with me at first,but I was able to persuade him
He was able to leave Europe before the war began Must 的用法:
必须,应该,如:
Must I
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