情态动词讲解

情态动词讲解

定义：情态动词表示说话人对动作的态度，比如：需要，可能，意愿，猜测或者怀疑等等。情态动词本身有一定意思，但不完全，不能单独作谓语，必须与动词原形连用。否定句中，在情态动词后面加not。

情态动词有：must, shall, should, had better 词形无变化 can(could), may(might),

will(would) 词形有变化need既可以是情态动词，也可以是实义动词，具有双重性。

一、can 表示 “能会”，否定为：can’t = can not = cannot 过去式为：could→couldn’t

(1) 表示会做某事，有能力做某事。意思 = be able to

e.g. He can speak English, but he___________ speak Japanese.

= He _______ _______ _______ speak English, but he isn’t able to speak Japanese.

I ___________ smile but I ____________ speak when I was 2 months old.

= I ______ ______ _____smile but I _______ able to speak when I was 2 months old.

区别：① can只用于现在时和过去时(could), be able to 可用于各种时态。

e.g. They will be able to tell you the news soon.

② be able to 不与can连用，但可以和其他情态动词或助动词连用。

e.g. He may be able to speak English very well some day in the future.

He may can speak… He can be able to speak…..

(2) 用于征求意见Can /Could /May /Might I(we) go now ?

Yes, you _______ . / Of course you _______.—No(Sorry), you _______. /_______.

注意：①此处的could和might都不表示过去，只是语气上的委婉，不用作回答。

②否定回答中，表示对他人造成一定伤害或影响，或表示违反了某种规定或法律时

用mustn’t较好。 May I smoke here? —I’m afraid you ______________ .

Could I take the book out of the library? —Sorry, you ______________.

③表示过去能力时，could 提问，只能用could回答。

Could you ride a bike when you were 4 years old? —No, I ______________.

(3) 表提出意见或请求 Can/Could you (please) do sth? = Would you (please) do sth?

（此句型中some 不变any）

e.g. Could you please give me a hand? Would you please pass me some salt?

(4) 表示允许或承诺 =may You can /may come and find me at any time tomorrow.

(5) 表示有一定把握的推测，用于否定句和疑问句。 肯定句用must。

表示没有把握的推测，用may /might。

The window is broken. Who did it? It _______ _______ (可能是)Mary. It _______ ______(不可能是) Mary. It _______ _______(一定是)Bob. I saw him go

into the room just now.

二、may 表示“可以，可能”，否定形式may not

(1) 表示没有把握的推测，“可能，也许”。

e.g. He may have a lot of work to do. = Maybe he has a lot of work to do.

You may be right. = Maybe you are right.

(2) 表示请求 “我可以……吗？” 表示许可 “你可以……”You may /can go now.

______ I use your pen? Yes, you may. / Yes, please. No, you _______. /_______.

三、must 表示“必须，肯定，一定”， 否定形式mustn’t = must not

(1) 表示必须，意思同have to Must I do it now? Yes, you must.

No, you don’t have to. / No, you _____________. (注意：否定回答不用mustn’t)

Children mustn’t play on the road because it’s too dangerous. (mustn’t只表“禁止”)

He doesn’t have to go away from here. =He ______________ leave here.

区别：①must表达主观意愿的“必须”，have to表达客观上或按道理说“不得不”。

e.g. I must study hard. It’s too late. I have to go now.

②must 没有人称和时态的变化，而have to有。

e.g. He had to walk back home because he lost all his money.

Mom will be away for a week, so we will have to do the cooking by ourselves.

(2) 表示有把握的肯定句中的推测，“肯定，一定”，见“一、（5）”

四、need 表示“需要”，否定形式needn’t = need not

(1)作情态动词，仅用于否定句和疑问句。

He needn’t go home early yesterday. = He didn’t need/have to go home early yesterday.

Need I call him right now? —Yes, you must.(注意：肯定回答不用need)

—No, you needn’t. /No, you don’t have to.

(2)作实义动词，need sth./sb.

need to do sth. 否定形式don’t need to = don’t have to 表示“不必”

e.g. I need some help. He needed to go home early yesterday.

Do I need to call him right now? Yes, you do. / No, you don’t.

五、should 表示“应该”，否定形式 shouldn’t = should not e.g. We should try our best to help the poor little girl. You shouldn’t be lazy.

六、had better do表示“最好是做……”，否定形式 had better not do

e.g. You’d better not drink so much coffee.

七、would 表示意愿

常见句型：①表请求Would you please do…? OK…. / Sorry, ….

②Would you like sth? Yes, please. / No, thanks.

Would you like to do sth? I’d love to. / I’d love to, but….

(注意：以上句型中，some不变any)

I.填空：

1.Mum，may I watch TV now？Sure, but you ________ finish your homework first .

2. ________ I read the article again？No，you needn't.

3. Can you go skating with us this afternoon？Sorry，I can't. I ________ take care of my

little sister at home.

4. Must I hand in my exercise book today？No，you ________.

5. May I talk with you？No，you ________. I'm busy today.

6. ________I have your English name， please？Yes， Helen. H-E-L-E-N.

7. Who is the boy over there？Is it John？No， it _______ be him. John is much taller.

8. Can you play baseball，Jay？Yes， I ________. It's easy.

9.You must come back every month. Yes， I ________.

10. ________ he swim ?Yes, he _________. But he ________ swim two months ago.

11. Must we clean the room right now？No， you________. You _________clean it

after lunch.

12. John________ come to see us tonight， but he isn't very sure yet.

13. Children ________ play with fire.

14. -________ I come in， Mr Green？Yes,come in， please.

15.Tom said he ___________ help me with my English.