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情态动词和虚拟语气情态动词表示说话人的语气或对事物所持的态度情态动词有一定的词义,但不能单独做谓语情态动词没有人称和数的变化,后面应接动词原形
1.can与could⑴表示能力,“能,会”We canuse thecomputer now,but we couldnt lastyear.be ableto dosth.表示有能力做某事,并且做了2表示请求或允许,在口语中可以用代替may,但比can正式—May/Can Icome in—Yes,you may/can.表示请求,口语中常用could代替can,使语气,但主要用在中,答语不能用could,应该用-Could Iuse yourpen-Yes,you can.或一No,I amafraid not.⑶表示推测,常用在或中I sawhim justnow.He canthave goneto Beijing.You couldnlhave leftit onthe bus.4表示客观可能性,表理论上的可能Il isusually verywarm inApril,but itcan berather coldsometimes.⑸表示惊讶,常用在否定句和疑问句中How canyou be so stupidHow couldyou dosuch asilly thing6cannot...too...can never...too...意思是_________________________You cantbe toocareful withdriving.2^may与might⑴表示请求或许可,“可以,may比can正式—May/Can Igo now—Yes,you may/can.might比may语气,没有时间上的区分但在might引起的疑问句中,答语不用might,应该用-Might/May Ihave alook-Yes,you may.或Yes,please./Certainly.No,you mustnt.或No,youd betternot.⑵表示推测,“可能”might比may语气He may/might haveknown thenews.3在机关、学校等的文书、公告中,表示“不得……”,,禁止……”,可以用或You maynot smokein theclassroom.⑷might aswell和may aswell意思是You may/mighl aswell doit atonce.5may well“”They maywell win.
3、must⑴mus[表示“必须,应当,mustnt禁止”Soldiers mustobey orders.过去、将来、完成等时态中表示“必须”时,可用的相应形式注意must疑问句的答语—Must Igo now—Yes,you must.—No,you neednt.No,you dont have to.⑵表示推测,用于肯定句,表示某事肯定会发生You mustbe verytired.He must have beentired.3表示不可避免性或肯定性,“必然要,必定会Man mustdie.4表示与说话人愿望相反及不耐烦,“Why mustit rainon Sunday
4、have to意思是“”,表示客观需要而must表示说话人的1donthaveio get up early.1had toget upearly.I willhave togetupearly.
5、shall与should lshoukl可用于if引导的虚拟条件句,表示语气较强的假设,“万一”If MrLi should have timetomorrow,wecouldask himquestions.2should表示义务、责任,“”We shouldstudy harder.3should表示推论、推测、可能性,“Dinner shouldbe readyby now.4should表示说话者对某事难以置信,感到惊讶,“竟然I amsorry thathe shouldbesocareless.
6、will与would⑴用于第二人称,表示询问对方或向对方提出请求语气更委婉Will yousend thisletter forme Wouldyou mindmy openingthe window⑵表示意志、决心和愿望I willnever do that again.They askedus ifwe woulddothatagain.⑶表示习惯性、倾向性动作,“”Fish willdie outof water.She wouldsit likethat forhours.
7、used to“过去常常”He used to gothere.否定形式He gothere.He gothere.He gothere.(不常用)would“过去常常……”表示过去的状态,只能用,不能用would Thereusedto be abig treein myyard.
8、need与dare可作实义动词、情态动词⑴作实义动词时:need“需要”She needsto bemore careful.dare“敢,敢于She daresto go out at night.二者均有的变化dare做实义动词时She dareslo goout atnight.She doesntdare togoout atnight.She doesntdare gooutatnight.⑵作情态动词时:need“需要”,没有的变化dare“敢,敢于,没有人称和数的变化,但有过去式dared
(3)need与dare用作情态动词时,主要用于,一般不用于肯定句⑷-Need1conic-Yes,you must.No,you neednt.
9、ought to应该”,语气比should重否定形式_____________________________You oughttobecareful.You oughtntto havelet outthe secret.
10、had better”最好(做)...”We hadbetter gonow.
11、情态动词+have done的用法
(1)表示对过去事情的推测musthave done用于can have done用于和句may/might have done一般用于和句中
(2)表示对过去未实现的事情感到后悔、责备或遗憾could havedone mighthavedoneshouldhavedone wouldhavedone虚拟语气Lif虚拟条件句时间If条件句主句过去had donewould/should/could/might+havedone现在were/did would/should/could/might+do将来did/werc would/should/could/might+do should do wereto do
2.wish时间从句谓语动词的虚拟形式as if过去had doneas though现在did/were将来would/should/could/mighl+do
3.if only句型中的虚拟语气与现在、将来相反would/could do与过去相反had done
4.would rather句型中的虚拟语气与现在、将来相反did与过去相反had done
5.without句型中的虚拟语气与现在、将来相反would/could/niight+did与过去相反would/could/might+had donedid
6.ifs high/about timethat+shoulddo。