情态动词概念：情态动词和不带to的动词不定式一起构成谓语，但ought除外。情态动词有一定的词义，没有人称和数的变化。它表示说话人的语气或情态，如请求、命令、愿望、能力以及可能性等。本文|由职业培训教育网独家整理。

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英语的情态动词有：

can, could

may, might

must

ought to

shall, should

will, would

dare, dared

need

1. can, could

(1) 能，能够、会、可以

Energy can be changed from one form into another.

We can buy a car by installments.

(2)许可

You can ( = may) go home now.

(3)表怀疑，难以置信

He couldn't (can't) be her father; he is too young.

(4) could + have + p. p.(过去分词)

He could have passed the exam.

(5)be able to是can的同义结构

Thus, we shall be able to determine the amount of alcohol burned.

They have not been able to come.

2.may , might

(1)允许、请求

Excuse me, may I have a glass of water?

(2)可能，或许;用might语气更加不肯定

These ideas may seem strange to you.

He might get lost.

(3) may (might) + have + pp表对过去的推测

She may (might) have missed the bus.

(4)表祝愿

May all your dreams come true.

May it be so.

(5) be allowed to是may的同义结构

You will be allowed to use this computer.

3.must

(1)必须，应该

The auditor must conduct sufficient verification.

(2) must not意为“不许”，“禁止”;must的否定回答为needn’t，表示“不必”的 意思。

We must not be afraid of difficulties.

Must I return the book.? —Yes, you must.

—No, you needn't.

(3) must + have + pp 表对过去的推测

I can't find my umbrella. Someone must have taken it.

(4) must + be + -ing 一定在

They must be talking about us now.

(5)have to是must的同义结构

We will have to change our plan.

4.ought to

(1)应该

We ought to make the most of our time.

(2)ought to + have + pp 表过去本来应该完成，但没有完成的事

She ought to have come to see me two days ago, but she forgot.

(3)表推测

This arrangement ought to please them.

5.shall

(1)征求意见

--Shall I close the door?

--Yes, please.(No, please don't.)

6.should

(1)应该

A formal written appraisal should be prepared annually.

(2)推测

They should be home by now.

(3)should + have + pp 表过去应做但没做的事。含有责备的意思。本文|由职业培训教育网独家整理。 

This conclusion should have been double-checked.

(4)表愤怒，不满，失望

I am very sorry that he should be so careless.

(5)用于让步从句中

He run away lest he should be seen.

7.will

(1)请求

Will you lend me your dictionary?

(2)自然规律，习惯动作

Fish will die out of water.

Water will boil at 100 degrees centigrade.

8.would

(1)委婉请求或命令

Would you take a seat?

(2)表过去习惯性动作

He would sit there for hours, doing nothing.

9.dare ,dared

(1)敢

How dare you speak to me like that?

No one dared speak of it.

(2)有时后面跟不定式，用作行为动词

He dares to think, to speak, and to act.

10.need

(1)“需要”，用于否定句和疑问句中

Need I show you my passport? --Yes, you must.

--No, you needn't.

We didn't need to call the doctor.

(2)needn't + have + pp 本不必做

She needn't have watered the flowers.