高考英语复习语法知识专题讲解9---情态动词(解析版)

高考英语复习语法知识专题讲解

专题九情态动词

情态动词本身有一定的词义，但需和其他动词一起构成谓语，除ought, used外，情态动词后面接动词原形。情态动词中have to可以用have got to 代替；need,dare也可用实意动词；used to 有两种否定形式：used not to和did not use to.

can, could 表示具有某种能力，指有能力做某事He could swim when he was five.

By the age of seven he could write beautifully.

表示请求和允许，和may相近；

口语中可用could表示委婉语

气，但回答时仍用can

－Could/Can I use your pen?

－Yes,of course you can.

Could I ask for your reaction to this policy?

表示推测，常用于否定句和疑问句中

Mike can't have found his car, for he came to work

by bus this morning

I think the work can be completed ahead of time. 表示“有时也会” It can be quite windy there, especially in spring. cannot but do sth.表示“只好，不得不” Father cannot but agree with his daughter's

opinion.

can't help doing sth. 表示“禁不住做某事” I can't help feeling sorry for the poor man.

The film is so impressive that we can't help crying.

be able to be able to 可以有多种时态，如：将来时

（will be able to), 完成时（have/has/had

been able to)

I will be able to speak French in another few

months.

I have been able to swim since I was 5.

be able to 侧重通过努力成功做成某事的

能力

He said he could swim across the river.

(指本身具有这种能力）

At last he was able to swim across the river.

(指通过努力做到了）

表示允许、许可或征求允许，否定回答

－Might/May I smoke in this room?

－No, you mustn't.

may, might 时要用 mustn't; might 比may 语气委婉－May/Might I take this book out of the room?

－Yes, you can. (No, you mustn't.)

表示可能性，might比may可能性更小

I think the trip may give me time to calm down.

An active volcano may explode at any time.

Don't go too far afield or we might lose you. may/might as well do sth.“不妨做某事，

还是做某事为好”

Everything is ready. We might as well start now.

will, would 表示意志、决心或愿望We will do our best to save the child.

I told her to stop crying, but she just wouldn't

listen.

用于第二人称，表示请求、建议等Will/Would you please post the letter for me?

Won't you take off your coat?

will表示“总是，惯于”；would表示过

去的习惯，意为“过去常常”

When he was a child, he would often go skiing.

He would sit there for hours sometimes doing

nothing at all.

表示推测或猜想This will be the house you're looking for.

I think he would accept the invitation.

shall 用于第一、人称的疑问句中，表示征求

对方的意见或请示

Shall I clean the desks one by one?

用于第二、人称的陈述句，表示说话者

的命令告、许诺等语气

He shall return that book tom

I shall think it over and let you know my idea.

You shall fail if you don't work harder.(警告）

用于第三人称，在条约、规定、法令等

文件中表示义务或规定，意为“应该，

必须”

Candidates shall remain in their seats until all the

papers have been collected.

Persons under 18 shall not be employed in night

work.

should, ought to 表示“应该”，用于表示现在或将来的责

任或义务：还可表示推测，指有一定依

据的推测

We should/ought to help each other and learn from

each other in our work.

We ought to go and see Mary tomorrow, but I don't

think we will.