不定式

作主语不定式直接置于句首,或采用先行词,将不定式后置.Tohesitateisapity.Tobehereisagreatpleasure.Itisapitytohesitate.It’sagreatpleasuretobehere.•后置不定式结构也适用于谓语动词不是连系动词的句子。•ItmademehappytofindMarythere.•Wouldn’titbeapitytospoilyourdrawing?•Howexcitingitwastofightashark!•不定式结构作主语通常表示具体动作,间或也可表示抽象动作,这一点与-ing分词结构作主语恰恰相反。•用作主语的不定式结构的逻辑主语通常可以在特定上下文或情景中看出,也可以由”for+名词词组”.间或也可用for+theretobe表示。•ItisimportantforustohaveagoodgraspofEnglish.•Itisagreatpleasureforustobeherethisevening.•It’sapityfortheretobeanydisagreementinthefamily.（在这种结构中，there后面的不定式只能是tobe）•不定式结构作主语不定式在联系动词后作主语补语有两种情况：一种情况，主语和主语补语都是不定式，其含义一是条件，一是结果。•Toseeistobelieve.Todecideistoact.另外一种情况，主语是以aim,ambition,duty,hope,idea,intention,mistake,plan,purpose,suggestion等为中心的名词词组，或以what引导的名词性分句，后面的不定式说明其内容。•Myideaistoclimbthemountainfromthenorth.•WhatIwouldsuggestistostartworkatonce.•不定式结作主语补语时常带to，但在某些句型中可省略to，条件是主语部分必须具有一个动作动词do。•AllIdidwasemptythebottle.•Theworstyoucandoisbecomeverydrowsy.•TheonlythingIcandonowisgoonbymyself.•WhatIreallywantedtodowasdriveallnight.(也有人指出在由what引导的主语分句中，如果谓语词部分的do是完成体形式，后面的补语也可以用-ed，如果do是进行体形式，则补语必须用-ing分词。)•Whathe’sdoneis:spoilthewholething.tospoilthewholething.spoiltthewholething.•Whathe’sdoingisspoilingthewholething.•Allsheseemstodoisgossipwithherneighbors.•不定式结构作动宾，能用带to不定式作宾语的有两种；一种是直接跟有带to不定式，另一种是跟有疑问词+带to不定式结构。•第一种常见的词有；afford,agree,aim,apply,arrange,ask,choose,claim,decide,decline,demand,desire,determine,expect,hope,learn,•long,manage,offer,pretend,promise,refuse,•seek,swear,threaten,want,wish,etc.•Heagreedtosmokenomorecigarettes.•Sheappliestoworkonlyatweekends.•afford通常与can,此同时can’t或它们的过去时形式连用。如：•Wecanaffordtopayforit.•Wecan’taffordtogoawayforaholidaythissummer.•第二种常见的词有decide,findout,forget,inquire,know,learn,remember,see,settle,think,consider,understand,wonder,tobecurioustoknow,etc.疑问词可以是what,where,who(m),when,how,whether,which,etc.(why除外)。如：•Idon’tknowwhattodo./wheretogo/who(m)toask/howtogetthere•Shedidn’tknowwhichonetobuy.•Wemustfindoutwhattodonext.•有些双宾语及物动词，也能用疑问词+带to不定式结构作直接宾语。•Pleaseinformmewheretogettheticket.•Ishowedthemhowtodoit.•此外，如果作宾语用的带不定式结构有自己的补语，就得用先行词代表它，把不定式置放到补语后。如：•Doyouconsideritwisetointerfere?•Hedeemedithisdutytohelp.•Icountitagreathonourtoservethepeople.•不定式结构一般不可以作介宾。只有在含有否定意义的带有介词except的结构中才能这样用。如：•IninformalEnglish“may”israrelyusedexcepttoexpresspossibility.•Hewilldoanythingforyouexceptlendyoumoney.•当but用作except解释时，其后也可跟不定式结构.•Theycoulddonothingbutwaitforthedoctorstoarrive.•不定式结构作宾补•1）see,hear,feel,watch,notice,observe等表示感觉的动词。不定式结构都不带to•Iheardhersing.•Thepolicemanobservedthemanopenthewindow.•Ifeltsomethingcrawlupmyarm.•2)have,let,make,advise,cause,allow,ask,beg,drive,encourage,expect,forbid,force,get,intend,invite,permit,persuade,remind,trust,urge,want,warn,etc.表示“致使”等意义的动词。除了have,let,make以外，都带to不定式结构作宾语补语。如：•Whatwouldyouhavemedo?•Youmademelaugh.•Ican’tgethertotalk.•Thenoticewarnedusnottogointothefields.•3)consider,declare,find,(=consider),prove,think,know,believe,discover,feel(=think),imagine,judge,suppose,understand等表示心理状态的动词。如：•Weconsiderhimtobeagoodteacher.Wethoughthertobequiteaclevergirl.•Wefoundhimtobedishonest.•Wejudge/believe/knowhimtobereliable.•在consider,declare,find，prove,think,etc.动词后的往往可以省略。但是，如果不定式是完成体形式，就不能省。如：•Weconsiderhim(tobe)foolish.•Weconsiderhimtohavebeenfoolish.•4)love,hate,like,prefer,want等表示情感状态的动词。•I’dlovethemtocometonight•I’dlike(for)youtocomedownhere.(AmE)•5)arrangefor,askfor,longforpreparefor,providefor,votefor,waitfor,callupon,counton,relyondependon,etc。如：•Iwillarrangeforyoutocome.Wewaitforthattobedone.Youcan’trelyonhimtoassistyou•YoucanalwaysdependuponJohntobetherewhenheisneeded•动词+宾语+不定式的被动态转换形式•上面五种动词，除了第四种，其它都可转为被动态。担有几点要注意：•1）第一种动词（除notice,watch不用于被动态外）转为被动态时，后面不带to不定式转为带to不定式。•Wesawthecarstop.•Thecarwasseentostop.•2)第二种动词（除了have）转为被动态，其后常用带to不定式.•Theymadeuswaitoutside.•Weweremadetowaitfortwohours.•只有let跟有单音节不定式时属于例外.•Theprisonerswereletgo.•但常用beallowedto代替.•Theywon’tletusgo.•Wewon’tbeallowedtogo.•3)第三种tobe省略与否，与主动结构相同.•Weconsiderhim(tobe)verycapable.•Heisconsidered(tobe)verycapable.•Weknowhimtobeagoodworker.•Heisknowntobeagoodworker.保(know的现在完成体否定形式为主动态时，后面接不带to的不定式。转为被动态时接带to的不定式。如：•Ihaveneverknownhimbehavelikethis.•Hehasneverbeenknowntobehavelikethatbefore.•4)第五类动词，有些有被动态，有些没有。有些被动态体现在不定式结构上。如：•Hewasseldomcalledupontospeakatthesegatherings.•Hecanbereliedontohelpus.(必须带can或could，否则不能转为被动态）•Weasked/arranged/longed/waitedforthattobedone.(但类似Iwillarrangeforyoutocome.这样的句子就无被动态。)•不定式结构作名词修饰语，不定式与所修饰的名词中心词，有时有主谓或宾关系。如：•Thisisthebestbookonthesubjecttoappear(=thathasappeared)thisyear.•Hehasalargefamilytosupport(=thathemustsupport).•在处于动宾关系时，如果不定式是不及物动词，其后得加上一个所需的介词。•Iwritewithapen.Iuseapentowritewith.•Isthereanyonetotalkto?•Youhavegivenmemuchtothinkabout.•不定式结构作状语表示目的，结果，原因，条件等。•Iamsavinguptobuyacomputer.•Shestoppedathometohelphermother.•Now,it’llbecoldupthere,sowe’dbettertakeblanketstowrapourselvesin.•另为了强调不定式结构表示目的，尤其在其前有否定词not时，通常在to之前加inorder/soas.•I’mattendingcollegeinordertolearn.•Heshoutedandwavedsoastobenoticed.•此外，表示目的的不定式可置于句首。在其前可加inorder，但不能加soas.•2)表示结果.如:•WhathaveIdonetodes