情态动词

情态动词的特征⑴情态动词本身有词义，但词义不完全。因此不能单独作谓语，只能和动词原形一起构成谓语。⑵情态动词后接的动词不定式一律不带to。⑶情态动词不随人称和数量的变化而变化。情态动词can和could的用法⑴表“能力”Canyoulifttheheavybox?⑵表“许可”HesaidIcouldborrowhisbike.⑶表“怀疑”“可能性”Whatonearthcanthismean?⑷表“猜测”①can用于疑问句、否定中，must用于肯定句中Canhebeinthelibrary?Hecan’tbeinthelibrary.Hemustbeinthelibrary.到②could+have+过去分词，表示本来能做到，但事实上未做到Hecouldhavefinishedthetaskontime,buttheheavysnowcameCanhehavesaidso?③can/couldnot+have+过去分词，表示本来不能做到，但实际上已经做了。Shecouldnothavecoveredthewholedistance,butinfactshearrivedaheadoftime.Shecannothavesaidsuchafoolishthing.注意：①could代替can，表示语气较为婉转。Couldyouhelpme?Yes,Ican.注意回答不用could。②can(能够)=beableto(仅表示能力时)，但beableto表示经过一番努力后才能做得到，且有更多的时态。Hewasagoodswimmer,sohe____swimtotheriverbankwhentheboatsank.A.couldB.mightC.shallD.wasableto情态动词may和might的用法⑴表“询问”May/MightI…?(CanI…?)⑵表“允许”Youmaytaketheboythere.Hetoldmehemightcome.（might与told相呼应）⑶表“可能”“或许”I’mafraidhemightnotlikethisplay.⑷表“猜测”①may/might+动词原型：表示对现在事情的猜测。Becareful,youmaybreakit.②may/might+have+过去分词：表示对过去事情的猜测，认为某事“可能”发生。Hemay/mighthaveplayedtheelectricgameonTVthewholenight.(Forhelooksverysleepy.)注意：①mayI…?的答语。肯定：Yes,youmay.否定：No,youmustn’t.No,youmaynot./No,you’dbetternot./No,youcan’t.②may/might/can/could用于目的状语从句中。Theemperorgavethemsomegoldinorderthat/sothattheymightbegintheirworkatonce.情态动词must和haveto的用法⑴表“必须”must（主观看法）必须，没有过去式。可用于间接引语中。haveto（客观需要）不得不，有多种时态。⑵疑问句及答语中MustI…?Yes,youmust./No，youneedn’t./No，youdon’thaveto.Doyouhaveto…?Yes,wedo./No,youdon’thaveto.⑶带must句子的反意疑问句中。①陈述部分must表示“必须”或“禁止”时：Hemustdoitalloveragain,mustn’the?Youmustn’twalkongrass,mustyou?②陈述部分must表示“必要”时：Wemustfinishtheworkinanhour,needn’twe?③陈述部分must表示“一定”“想必”等推测含义时，要根据陈述部分的不定式结构，在附加疑问部分采用与其相适应的主动词或助动形式。1）Youmustbehungrynow,aren’tyou?(Youmustbehungrynow.=I’msureyouarehungrynow.)2）HemustbewatchingTVnow,isn’the?(HemustbewatchingTVnow.=I’msureheiswatchingTVnow.)3）Tommusthavelivedhereforalongtime,hasn’the?(Tommusthavelivedhereforalongtime.=I’msureTomhaslivedhereforalongtime.4）Shemusthavearrivedyesterday,didn’tshe?(Shemusthavearrivedyesterday.=I’msureshehasarrivedyesterday.)情态动词should和oughtto的用法⑴表“应当”should表示劝告,建议Youshouldlistentothedoctor’sadvice.ought表示“有义务或有必要”做某事Yououghttofinishyourworkbeforeyougohome.⑵表“可能”的猜测.“可能、该”对现在情况﹑将来情况或过去情况的某种推测Theyshouldhavefinishedtheworkbytomorrow.Theyshouldgethomebynow.⑶表“责备”或“惋惜”should/oughtto+have+过去分词:该做,没有做shouldnot/oughtnotto+have+过去分词:不该做,做了⑷表“竟然”“竟会”Ican’tbearthatheshouldspeakillofme.Itisamarvelthatsheshouldhavesurvivedthedisaster.注意：①should在虚拟语气中的使用Shouldheactlikethatagain,hewouldbepunished.②oughtto的疑问式及否定式Oughthetogo?Yes,Ithinkheought(to).(oughtnottodo/oughtn’ttodo)情态动词need和dare的用法⑴need,dare在疑问句或否定句中用作情态动词。Heneednot(needn’t)go.Needwedoitagain?No,youneedn’tdoitagain.Hedarenotsayso.Dareshegooutaloneatnight?HowdareyousayI’munfair?⑵need,dare在陈述句,疑问句,否定句中,后加行为动词的不定式。Heneedstogo.Hedoesn’tneedtogo.Doesheneedtodoitagain?No,hedoesn’tneedtodoitagain.Hedarestosay.Hedoesn’tdare(to)say.⑶needn’t+have+过去分词:表示本来不必做,但做了。Sheneednothaveattendedthemeetingyesterday,butshedid.情态动词shall和will的用法⑴shall和will在疑问句中的用法shall用于征询对方意见或请求指示,用在一三人称ShallI(’ve)…?Shallhe/she…?WhereshallI/wewaitforyou?will用于询问对方的意思或向对方提出要求,一般用于第二人称Willyou(please)…?Won’tyou…?Wouldyouliketo…?Won’tyougoandseethefilm?Yes,IthinkIwill.⑵表示强烈情感时的用法shall表示说话人的意愿,有“命令”“警告”“强制”“允诺”等,用于第二、三人称,要重读。YoushalldowhatItellyou(todo).Everythingshallbedonetosavetheship.will表示“意志”“意愿”,用于各种人称。Iwon’tdoanythingyoudon’tlike.would表示过去时间的“意志”“愿望”。Shylockwouldnottakethemoneyearlier.(3).Will用于非人主语时，表示固有性质，倾向Thewindowwon’topen.Thedoorwon’tshut.情态动词usedto和would的用法⑴usedto和would的区别usedto表示过去的动作和状态,重在和现在情况的对比。Iusedtoplaycardsalot,butnowIseldomplay.Myhometownisnotwhatitusedtobe.would只表示过去动作的重复,现在的情况不明。IwouldgotoseemygrandfatheronSundaywhenIwasinthemiddleschool.⑵相同点:表示过去的习惯,可互换。注意：usedtodo的否定式usedn’ttodo/didn’tusetodo疑问句Didyouusetodo?Usedyoutodo?否定句Didn’tyouusetodo?Usedn’tyoutodo?情态动词•hadbetter=mayaswell,wouldrather•hadbetter/mayaswell/wouldratherdo