浙江省杭州市塘栖中学高中英语必修三教学课件：B3U1 GRAMMAR 情态动词.ppt

1、GrammarModal verbs 情态动词(I)Unit1 Festivals around the world情态动词的语法特征1）情态动词 不能单独做谓语，除ought 和have 外，后面只能接动词原形。2）情态动词没有人称，数的变化，但有些情态动词，如can、will也有一般式和过去式的变化。3）情态动词的“时态”形式并不是时间区别的主要标志，不少情况下，情态动词的现在式形式和过去式形式都可用来表示现在时间、过去时间和将来时间。情态动词用法例句can/could表“能力”Some of us can use the computer now,but we couldnt ten y

2、ears ago.注意:can与be able to 区别表“许可”1.Can I sit here?2.-Could I have a look at your book now?-Yes,you can./No,you cant.注意:can 与could区别can,could 和be able to的用法She can/is able to sing the song in English.This machine can make you feel comfortable.1.can,be able to都可表示“能力”can的主语是人或物,be able to的主语是人Well be

3、 able to finish the work soon.I havent been able to see the film.2.can只用于现在式和过去式(could)。be able to可以用于各种时态。3.表示特定的某一过去能力或表示成功地做了某事时，只能用was/were able to,不能用could。He was able to flee Europe before the war broke out.He was able to swim halfway before he got tired.1.-Look,someone is coming.Who can it be

4、?-It may be Mr.Li.-It cant be him.He has gone to Shanghai.表示推测，译为“可能、或许”，can常用于否定句(意思是“不可能”)和疑问句；could可用于肯定句，否定句和疑问句。情态动词用法例句may/might表许可-May I use your pen?-Yes,please./No,you mustnt.表祝愿May you be happy.表可能He may be a teacher.情态动词用法例句must/have to 表义务-Must I finish my work now?-yes,you must./No,you

5、neednt/dont have to.注意：must 与have to区别表推测He must be a teacher注意；只用于肯定句I dont like this TV set.We must buy a new one.There was no more bus.They had to walk home.2.表示“必须”这个意思时，must 和have to 稍有区别。must着重说明主观看法，have to 强调客观需要。另外，have to 能用于更多时态。He must be joking.There is nobody here.They must have all go

6、ne home.3.must表示对某人某事的猜测，作“准是”，“一定”，一般用于肯定句中。对过去发生的事情作肯定判断用must have doneAt a time when everybody was in bed,he mustturn on the TV.4.must表示“偏要，硬要”，指做令人不快的事情情态动词用法例句shall表示征询意见Shall I open the window？用于第一、三人称的疑问句表许诺，警告，命令，决心等1.You shall do as I ask you to do.（命令）2.Don t worry.You shall get the answer

7、 this afternoon.(许诺)3.You shall be sorry for it one day.（警告）用于第二、三人称shall,should 和ought toYou shall do as I say.(命令)Tell him that he shall have the book tomorrow.(允诺)Nothing shall stop me doing it.(决心)1.shall用于第二、三人称表示允诺、警告、命令、决心等。Shall I open the window for you？（征求意见）Shall he fetch some water for y

8、ou？（请求）2.在疑问句中,用于第一、三人称，用来表示请求或征求意见。Young people should learn how to use computers.Every citizen ought to obey law.You ought not to go.3.should常表示劝告、建议、命令，与ought to意义相近，但ought to多表示责任、义务，语气强烈。在疑问句中通常用should代替ought to。情态动词 用法例句will/would表意愿I will help him if he asks me to.表示征询对方的意愿或提出请求1.Will you giv

9、e him a message when you see him?2.Would you mind my smoking here?表习惯She will sit for hours reading in the afternoon.When we were young,we would go swimming every summer.注意：用于第二人称的疑问句注意：与used to do 的区别would所表示的过去的习惯也许现在仍旧保持，而used to do所表示的“过去常常”，现在已经不再做这件事了。When he was young,he used to smoke heavily

10、.（暗示现在已经戒烟。）must have donecan have donecould have donemay/might have done表示对过去发生的事情的肯定推测，意为“一定已经”只用于肯定句It is 6 oclock.She must have comehome.表示对过去发生的行为的怀疑和不肯定通常用于否定句和疑问句could have done也可用于肯定句.I dont know why she didnt call me yesterday.Can/Could she have forgotten my number?常用于肯定句和否定句意思为也许已经.He seem

11、s to know the city quite well.He may have been there before.情态动词have done表示对过去发生的事情进行推测表示对过去发生的事情或动作责备或抱怨的语气should(ought to)have doneshouldnt have donemight have donecould have doneneed have doneneednt have done本应该做而实际上没有做You should have gone overyour lessons.You shouldnt have watched TV last night.

12、本不应该做某事而实际上做了本来可以做但实际上没有做you might have given him more help,though you were busy.本来能够做而实际上没做Why did you stay at a hotel when you went to New York?You could have stayed with Barbara.本来有必要做而实际上没做本来没有必要做而实际上做了You neednt have come to work.Its Sunday today.You should/ought to have told her the truth earlier.She shouldnt have left without saying a word.4.should/ought to have done表示责备或批评,意为“本应该做到但没有做到”,用于否定则表示“本不该但”ought to的语气更强烈.