情态动词(Modal Verbs),又称为情态助动词(Modal Auxiliaries),与实义动词连用表示说话人的语气,可表达建议、要求、可能、意愿等。常用情态动词列表如下:

情态动词没有人称和数的变化,即第三人称单数后的情态动词不加s。此外,情态动词的过去式多数情况下只表示语气,而不表示时间。

情态动词的用法很多,很繁琐。现就其几点重要的用法进行分析总结。

一、表示猜测

当表示猜测时,可以用might, may, must, could, can。具体用法如下(V表示适用):

例如:

A: (Pointing to a person standing far away) Who can / could it be?

肯定回答B: It might be teacher Li. 那可能是李老师。(语气很不肯定)

或It may be teacher Li. 那可能是李老师。(语气有点不肯定)

或It must be teacher Li. 那一定是李老师。(语气非常肯定)

否定回答B: It might not be teacher Li. 那可能不是李老师。(语气最弱)

或It may not be teacher Li. Teacher Li is not so tall. 那可能不是李老师,李老师没有那么高。(语气较弱)

或It couldn’t be teacher Li. Teacher Li was in the office just now.那不可能是李老师,李老师刚才还在办公室。(语气较强)

或It can’t be teacher Li. Teacher Li has gone abroad.那不可能是李老师,李老师出国了。(语气最强)

注意:如果表示对过去发生的事情的猜测,可用以上情态动词+ have +过去分词来表示。例如:

The ground is so wet. It must have rained last night. 地这么湿。昨晚一定是下雨了。

二、表示许可、必须和必要

当用情态动词表示许可、必须和必要时,可以用may, might, can ,could, must, need。具体用法如下:

注意:

1. 在这种用法中,同样might 和could也并不是表示may 和can的过去式,只是比may 和can语气更弱,更委婉。另外,can和could比may与might更加口语化。

2. need 作为情态动词一般只用于疑问句和否定句。在肯定句中,need 一般用作实义动词,固定搭配为need to do sth,表示"有必要、需要做某事"的意思。当然,need作为实义动词,照样有自己的疑问句和否定句(需要用助动词do)。

3. 在回答时要根据句意回答,不一定用提问的原词回答。另外,用might或could提问,回答不用might和could, 而要用may和can。

例如:

1. May I sit here? 我可以坐这儿吗？

肯定回答: Yes, please. 可以,请吧。

或Certainly. 当然可以。

否定回答:Please don’t. 请不要。

或No, you mustn’t. 不,不许。

2. Must / Need we hand in our homework now? 我们必须/有必要现在交作业吗？

肯定回答:Yes, you must. 是的,必须。

否定回答:No, you needn’t. 不用,没有必要。

3. Could I keep the book till next week? 我可以把书留到下周吗？

肯定回答:Yes, you can. 可以。

否定回答:No, you can’t. 不可以。

4. need 作为实义动词:

1) Do I need to leave my phone number? 我有必要留下我的电话号码吗？

肯定回答:Yes, you do. 是的,有必要。

否定回答:No, you don’t. 不,没必要。

2) You need to fill in your name here. 你需要在这里填上你的姓名。

三、某些情态动词+ have +过去分词的用法

needn’t have done 本来没必要做(但实际已经做了)

should have done 本来应该做(但实际没做)；竟然

should not have done 本来不应该做(但实际做了)

ought to have done 本来应该做(但实际没做)

ought not to have done 本来不应该做(但实际做了)

could have done 本来能做(但实际没做)

注意:

1. need作为情态动词,前面已经说过,一般不用于肯定句。在肯定句中,其一般为实义动词,要用need to have done。例如:You need to have finished it be-fore you come to my office. 你应该在来我办公室之前就把它完成。

2. could not have done 也已经在前面说过,它是"不可能做了某事"的意思,表示猜测,而不是"不能"的意思。例如:

1. You needn’t have run all the way here. It’s just 8:00. The meeting has been put off till 9:00. 你没有必要一路跑过来。现在才八点钟,会议已经推迟到九点钟了。

2. I didn’t know that he was sick. You should have told me about it. 我当时不知道他病了。你本应该告诉我的。

3. We were short of money. Other-wise, we could have finished it in time. 我们缺少资金。否则我们本来能够按时完成的。

4. I am surprised that he should have refused such a good job. 我很奇怪他竟然拒绝了这么好的一份工作。四级考试的听力部分经常会有大量的情态动词出现,平时注意积累学习它们的主要用法对以后的应试必然大有帮助。在今后的学习中同学还要用心多学、多练,这样才会融会贯通。

牛刀小试

1. Where ______ my key? I can’t find it.

A. could I have put

B. could I put

C. may I have put

D. may I put

2. —Mary said she had failed the English final exam. —It ___ be true. She is joking. She is so excellent.

A. may not

B. might not

C. can’t

D. couldn’t

3. The phone is ringing. It ______ be Tom.

A. has to

B. might

C. can

D. should

4. —Need I leave my phone number?—_______

A. Yes, you must.

B. Yes, you need.

C. Yes, you do.

D. Yes, you may.

5. I’m afraid I ______ come to your party next week.

A. can

B. can’t

C. must

D. should

6. My mother gave me a letter to post. I ___ remember to post it on my way to school.

A. can

B. could

C. might

D. must

7. I told Sally how to get there, but perhaps I ____ for her.

A. had to write it out

B. must have written it out

C. should have written it out

D. ought to write it out

8. I was really anxious about you; you _____ home without a word.

A. mustn’t leave

B. shouldn’t have left

C. couldn’t have left

D. needn’t leave

答案及解析

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