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用法usage情态动词许可,请求permissionandrequest可能推测possibilityandprediction义务，职责dutyandobligation意图，打算intention意愿，愿意Willingness 意志，决心determination andinsistencecan/could√√....may/might√√√...shall/should√√√√√√will/would√√.√√√must√√√...oughtto.√√...may/might√√√...shall/should√√√√√√will/would√√.√√√oughtto.√√...needdareusedtodosth情态动词的特点•情态动词有一定的意义•无人称和数的变化•通常不带to,后接动词原形•表示说话人的语气或情绪Whatare情态动词(modalverbs)?能力，才能abilityandcapability使用场合对现在和未来的推测对过去事情的推测√否定句、疑问句can/could+动词原形can/couldhavedone.肯定句、否定句may+动词原形may/mighthavedone.肯定句、否定句、疑问句用来表示一种估计的情况“按理会/估计会”should+动词原形shouldhavedone..肯定句must+动词原形musthavedone....过去常常做某事Whatare情态动词(modalverbs)?情态动词词义例句更多表达形式注意事项①表示能力（体力、知识、技能）Canyouliftthisheavybox?（体力）Marycanspeakthreelanguages.（知识）Canyouskate?（技能）I’llnotbeabletocomethisafternoon。（更多的时态）Hewasabletogotothepartyyesterdayeveninginspiteoftheheavyrain.（经过努力才得以做成功某）①此时可用beableto代替。②Can只有一般现在时和一般过去式；而beableto则有更多的时态。③当表示“经过努力才得以做成功某事”时应用beableto，不能用Can。was/wereabletoto表示成功做了某事②表示请求和允许，用could要比用can更加迟疑不决，当你没有把握得到允许时，这样更婉转。CanIgonow?CouldIcometoseeyoutomorrow?CouldIgiveyoudinneroneofthesedays?Yes,youcan.No,youcan’t.Yes,youcan.(No,I’mafraidnot.)Yes,ofcourseyoucan.（肯定回答句中，不能用could）在请求允许的用法中，could并不是过去时，它指的都是将来时，虽然请求用could语气委婉，也允许不用could.③表示客观可能性They’vechangedthetimetable,sowecangobybusinstead.Thishallcanhold500peopleatleast.④表示推测、惊讶、怀疑、不相信的态度，用于疑问句、否定句和感叹句中。Canthisbetrue?Thiscan’tbedonebyhim.Howcanthisbetrue?①can用于否定和疑问句(could不限)②can(be)表示有时候会（常与sometimes,attimes连用）①表示请求和允许，此时might比may语气更委婉，指的都是将来时而不是过去式。Might/MayIsmokeinthisroom?May/MightItakethisbookoutoftheroom?Yes,youcan./sure/certainly/ofcourse/Youmayindeed（不能用might）。No,youcan’t/mustn’t/maynot.①用MayI...？征徇对方许可时比较正式和客气，而用CanI...？在口语中更常见。②表示推测、可能性（不用于疑问句）。Hemay/mightbeverybusynow.Yourmothermay/mightnotknowthetruth.此意常用于肯定句。（might可能最小）③用于祈使句，表示祝愿。Mayyousucceed!固定句型为“May+主语+V原型”：①表示必须、必要；说话人“不许”和“禁止”某人做某事，有很强的劝告语气。Youmustcomeintime.Mustwehandinourexercisebookstoday?Yes,youmust.No,youdon’thaveto/youneedn’t.(否定句不能用mustn’t禁止，不准）②must是说话人的主观看法，而haveto则强调客观需Ireallymustgonow.IhadtoworkwhenIwasyourage.Must只有一般现在时，haveto有更多的时态形式。③表示推测、可能性（只用于肯定的陈述句）You’reTom’sgoodfriend,soyoumustknowwhathelikesbest.Yourmothermustbewaitingforyounow.只用于肯定句。在否定句/疑问句中用can/could①表示请求、建议等，would更委婉。Will/Wouldyoupassmetheball,please?Willyou？Willyougivemeapieceof此意用于疑问句，常与you连用②表示意志、愿望和决心。Iwillneverdothatagain.Theyaskedhimifhewouldgoabroad.Would此时为will过去式，无意义差别Whataremodalverbs?（什么是情态动词）cancouldmaymightmusthavetowillwould③would表示过去反复发生的动作或某种倾向;would表示过去习惯时比usedto正式，且没有“现已无此习惯”的含Duringthevacation,hewouldvisitmeeveryotherday.Thewoundwouldnotheal.叙述真理：Thetreewillleavewithoutwaterfor3months.④表示估计和猜想，对目前事物的预料。Itwouldbeaboutteno’clockwhenshelefthome.Thatwillbethepostmanringing.(would表示过去/现在；will表示现在/将来)①shall用于第一人称，征求对方的意见，意思是好不好。Whatshallwedothisevening?Shallthereporterswaitoutsideorwhat?Shallyoudosomeshoppingwithme?②shall用于第二、三人称，表示说话人给对方的命令、警告、允诺或威胁。Youshallfailifyoudon’tworkhard.(警告)HeshallhavethebookwhenIfinishit.(允诺)Heshallbepunished.(威胁)Passengersshallnottalkwiththedriverwhilethebusismovingshan't=shallnot（不应该（*只适用于英国英语）③表规章、法令、预言：“必须”Everycompetitorshallwearanumber用于所有人称should(与shalloughtto词义互通）①should,oughtto表示“应该”，oughtto表示义务或责任，比should语气重。Yououghtto/shouldpaymoreattentiontowhatyourlawyersays.Youshouldstayhereaslongasyoulike.Ishouldhelpherbecausesheisintrouble.Yououghttotakecareofthebaby.②表示劝告、建议和命令;should,oughtto可通用，但在疑问句中常用should。Youshould/oughttogotoclassrightaway.Youalwaysoughttocarrysomesparemoney.ShouldIopenthewindow?always,never,really可以放在ought前面和后面。前面比较常见。③表示推测时，should,oughtto(客观推测),must(主观推测)。Hemustbehomebynow.(断定他已到家)Heoughtto/shouldbehomebynow.(不太肯定)Thisiswheretheoilmustbe.(直爽)Thisiswheretheoiloughtto/shouldbe.(含蓄)Youaremistaken,Ishouldsay.(依我看你是搞错了)Thispenoughtto/shouldbeyours.(不太肯定)肯定的语气没有must用于推测时强①dare表示敢于，主要用于否定句和疑问句中和条件从句中,过去式形式为dared。HowdareyousayI’munfair?Hedaren’tspeakEnglishbeforesuchacrowd,darehe?Ifwedarednotgotherethatday，wecouldn’tgetthebeautifulflowers.Idaren’taskherforarise.Howdidyoudaretotellherthat?Iwonderwhetherhedarestandupinpublic.Idon’tknowhowshedarestowearthatdress.②need 表示需要、必须，主要用于否定句和疑问句中；在肯定句中一般用must,haveto,oughtto,should代替。NeedIfinishtheworktoday?Doyouneedanyhelp?Yes,youmust.No,youneedn’t.Youneedn’tcomesoearly.多用于肯定句:(sb.)needtodo/daretodo(sth.)needtobe/donewillwouldshallneeddareoughtto③dare和need作实义动词用时，有人称、时态和数的变化。在肯定句中，dare后面常接带to的不定式。在疑问句和否定句中，dare后面可接带to或不带to的不定式,而need后面只能接带to的不定式。Idaretoswimacrossthisriver.Hedoesn’tdare(to)answer.Heneedstofinishhishomeworktoday.①表示过去常常做某事,强调现在已经不存在的习惯,它只用于过去时态。Didyouusetogoswimmingintheriverwhenyouwereyoung?（你小时候经常在河里游泳吗?）Usedhegotoschoolbybike?（他过去骑车上学吗?）Iusedtogotothecinema,butIneverhavetimenow.Heusedtolistentopopmusicbutnowhelikesrockmusic.Youdidn'tusetodrink.（你过去不喝酒）Theshopusedn'ttoopenonSundays.（过去这家商店星期天不营业）肯定句式：主语+usedto+动词原形...否定句式：A)主语+didnotuseto+动词原形...B)主语+usednotto+动词原形...一般疑问句式：A)Did+主语+useto+动词原形...?②usedto用于省略句时，肯定式保留to，否定式不保留toUsedyouplaybasketball?（你过去常打篮球吗?）Yes,Iusedto.(No,Iusedn't.)（是的，经常打/不，不常打。)Idon'twritetohimnow,butIus