情态动词高三英语课件

modalverb情态动词有一定得意义，但没有人称和数的变化，不能独立使用，它和后面的动词构成谓语．只作情态动词的can/could,may/might,oughtto，must可情态可实义的need,dare/dared可情态可助动词的shall/should,will/would勉强作情态动词的haveto,usedtocan&could•can表能力(beableto表“经努力成功做”)客观可能性请求允许•could表委婉请求主要:疑问句,不用肯定句Couldyoudo…?Yes,Ican.(No,youcan’t.)•could虚拟语气但can不能•can/could表惊异,怀疑,不相信（否，疑）猜测may&might•表请求许可•MayIdo…?Yes,youcan/may.No,youcan’t/mustn’t.表“不可以”“禁止”•表祝愿Mayyousucceed!(倒装）•表推测（不用于疑问句）•Musttheydo…?Yes,theymust.No,theyneedn’t/don’thaveto.must&havetomusthaveto主观／客观主观客观时态现在，将来多种表推测√×询问意愿√×否定意禁止，不允许不必NeedIdo…?Yes,youmust.No,youneedn’t.dare&need情态动词实义动词dare否，疑，条darenotdo否,疑don’tdaretododon’tdaredo不用于肯定句肯：daretodoneed否，疑needn’tdo(don’t)needsth(don’t)needtodo肯：must,haveto,oughtto,shouldshall用于第一，三人称疑问句，征求意见或请求shall第二，三人称陈述句,命令,警告,允诺,威胁should表劝告，建议，命令，顺理成章的＝oughtto•疑问句中常用should代替oughtto•oughtto表应该，语气＞should•美语中，oughtto用于否，疑句时to可省shall,should&oughttoWill/Wouldyoudo…?表请求表意志，愿望，决心would表过去反复发生得动作或某种倾向“总是,总要”usedto表过去常常（现在已没有这种习惯）“过去常常”usedto可于状态动词连用would不可以eg.Heusedtobeaquietboy.()Hewouldbeaquietboy.()will&would√×可表推测的情态动词现在／将来:～do(can,could,may,might,must)过去：musthavedone=mayhavedone=mighthavedonecan/could(not)havedonecan/couldhavedone=shouldhavedone=oughttohavedoneneedn’thavedonedidn’tneedtodo=didn’thavetodo