情态动词用法一、can/could1.表能力（体力、知识、技能）。Canyouliftthisheavybox?（体力）Marycanspeakthreelanguages.（知识）Canyouskate?（技能）此时可用beableto代替。Can只有一般现在时和一般过去式；而beableto则有更多的时态。注：当表示“经过努力才得以做成功某事”时应用beableto，不能用Can。如：Hewasabletogotothepartyyesterdayeveninginspiteoftheheavyrain.2.表示请求和允许。-----CanIhaveawordwithyou?-----Yes,youcan./No,youcan’t.此时可与may互换。在疑问句中还可could,might代替，不是过去式，只是语气更委婉，不能用于肯定句和答语中。----CouldIcometoseeyoutomorrow?----Yes,youcan.(No,I’mafraidnot.)3.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?4.表示理论上的可能性，用于肯定句。常和sometimes,attimes连用。Itishotinsummerhere,butsometimesitcanbecool.5.用于句型：cannot/never…too…/enough…Youcan’tbetoocarefulwhiledriving.Ican’tthankyouenough.二、may/might1.表示请求和允许。might比may语气更委婉，而不是过去式。否定回答时可用can’t或mustn’t，表示“不可以，禁止”。1)----Might/MayIsmokeinthisroom?----No,youmustn’t.2)----May/MightItakethisbookoutoftheroom?----Yes,youcan.(No,youcan’t/mustn’t.)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）。might不是过去式，它所表示的可能性比may小。Hemay/mightbeverybusynow.Yourmothermay/mightnotknowthetruth.注：maynot可能不cannot不可能3.用于祈使句，表示祝愿。Mayyousucceed!=Wishyousuccess!4.may/mightaswell…./well…Youmay/mightaswellhavearest.Youmay/mightwellpasstheexam.三、will/would1.表示请求、建议等，would更委婉。Will/Wouldyoupassmetheball,please?2.表示意志、愿望和决心。Iwillneverdothatagain.Theyaskedhimifhewouldgoabroad.3will表示现在的习惯；would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”的含义。）Duringthevacation,hewouldvisitmeeveryotherday.Iwillhaveawalkafterluncheveryday.4.表示主语的某种属性。Thedoorwon’topen.Theenginewon’tstart.5.表示某种趋势。Withoutwater,fishwilldie.2.mustn’t表“禁止”Youmustn’tplaywiththeknife.3.(表固执、不满等)偏偏；硬要；偏要Ifyoumustknow,I’mgoingtohelphimlookforanapartment.Mustyouinterruptmenow?Mustyoumakealoudnoise?4.表肯定推测。must+v对现在的肯定推测;must+havedone对过去的肯定推测。Thelightison.Ourteachermustbeintheoffice.Thegroundiswet.Itmusthaverainedlastnight.Yourmothermustbewaitingforyounow.注:musthavedone的反义：can’t/couldn’thavedone五、shall1.用于一般疑问句中,与第一、三人称连用,表示征求对方的意见Shallwegooutforawalk?Shallhehaveatry?【注】may用于征求对方的许可,shall用于征求对方的意见或指示.MayIhavealook?我能看一下吗?ShallIhavealook?要我看一下吗?2.用于第二、三人称,表示说话人的命令、警告、强制、允诺、威胁或决心等Don’tworry.Youshallgettheanswerthisveryafternoon.Heshallbesorryoneday.Itellyou.3.用于法律、规则等条文中)应……,须……,得……Thefineshallbegivenincash.Accordingtotheregulations,thestudentsshallgotobedby10o’clockintheevening.六、should1.(表义务、责任)应该Weshouldattendthemeeting.2.表推测“理应”。Heshouldbehomebynow.3.(表惊讶、遗憾)竟然；居然Itwassadtomethatthey,sopoorthemselvesshouldbringmefood.4.表示感情色彩。常和how,why连用。HowshouldIknow?Whyshouldn’tyouinvitehim?5.用于虚拟语气中.Shouldyouhaveanyquestions,pleaseletmeknow.Isuggestthatyoushouldcomenow.Takeanumbrellaincaseitshouldrain.七、dare/need1.dare作情态动词用时,常用于疑...
