英语语法—状语从句

状语从句,1、本讲内容：学习状语从句。2、学习要求：（1）掌握状语从句的种类。（2）学会引导状语从句的从属连词。3、学习指导：（1）本讲重点：状语从句的种类。（2）本讲难点：从属连词之间的区别。,4、典型例题解析：,状语从句在主从复合句中修饰主句中的动词，形容词或副词，按意义可分为时间、地点、原因、目的、结果、条件、方式、比较、让步等状语从句。从句的位置放在句首，也可放在句末。放在句首时，从句后面常用一个逗号，放在句末时，从句前一般不用逗号。,1、时间状语从句：,引导时间状语从句的从属连词有：when,while,as,whenever,before,after,since,till,until,assoonas,once等引导。如：,Whenhewasstillayoungman,hewasforcedtoleavehishomelandforpoliticalreasons.Ithasbeen15yearssinceheleft.IlltellhimthenewsassoonasIseehim.Onceyouhavegotusedtoit,youwilllikeit.Iwaitedtillhehadfinishedhiswork.,注意：（1）when,as,whilewhen即可引导持续性动作，又可引导短暂性动作。它可以表示主句的动作和从句的动作同时发生，或从句的动作发生在主句动作之前。如：,WhenIwasaboy,IusedtogototheseashoreonSundays.（同时）Whenthelessonwasover,webeganourwriting.（从句动作在前）,as引导持续性动作，侧重主句和从句的动作同时发生。Hehurriedhome,lookingbehindashewent.Isawyoursisterasshewasgettingonthebusyesterday.Hesangashewalked.,While：指的是“在某一时间里”，“在期间”，从句里的动作必须是持续性的，它也强调主句和从句动作的同时发生，往往侧重主句和从句动作的对比。,如：WhilehewasinLondon,hestudiedmusic.WhilewewerewatchingTV,hewaswritingacomposition.,while也可做并列连词，表示对照的意思。如：,Heistallwhilehisbrotherisshort.,当when,as,while表示“在一段时间里”，主从句的动作同时发生时，可以换用。如：,While(When或As)wewerediscussing,Mr.Smithcamein.,（2）如果when和before引导的从句位于主句之后，有时不能译成“当时候”和“在之前”，而要译成“就”、“才”、“这时”等。如：,ThestrugglelastedfouryearsbeforetheNorthwonintheend.,Healmostknockedmedownbeforehesawme.Shehadnotbeenmarriedmanyweekswhenthemansawherandwasstruckbyherbeauty.IwaswalkinginthestreetwhenIsawhim.,(3)bythetime,eachtime,everytime,immediately,themoment,theinstant,theminute,soonafter,shortlyafter都可以作为连词，引导时间状语。如：,Bythetimehewasfourteen,hehadtaughthimselfadvancedmathematics.,Eachtimehecame,hewouldcallonme.Youmustshowhiminimmediatelyhecomes.IrecognizedhimthemomentIsawhim.,(4)till和until如果主句谓语动词是持续动词，通常用肯定式的主句，表示“直到为止”。如：Iworkedtill(until)hecameback.,如果主句谓语动词是瞬间动词，则用否定式的主句表示“直到才”。如：,Ididntgotobeduntil(till)hecameback.,放在句首表示强调时一般用until。如：,Untilhereturns,nothingcanbedone.,(5)、Since引导的状语从句从句通常用一般过去时而主句通常用完成时态或完成进行时态SinceIleftschool,Ihaveonlyseenhimonce.IthasbeenrainingeversinceIlostmyjob.“Itsince”句型中，主句的谓语动词常用一般现在时。Itseightyearssincehegotmarried.他结婚八年了。,(6)、assoonas,hardly-when,nosooner-than,themoment等表示“一-就-”Assoonashecamehome,itbegantorain.Themomenthecamehome,-HehadhardlycomehomewhenitbegantorainHardlyhadhecomehomewhenitbegantorain.Nosoonerhadhecomehomethan-,（7）时间状语从句中谓语动词不能用任何一种将来时，只能用现在时和过去时表示将来时。,2、地点状语从句：,通常由连词where和wherever引导。如：,Gobackwhereyoucamefrom.Whereveryougo,youmustwritetoyourparents.Wherethereisawill,thereisaway.Wherethereistoomuch,thepoisonandwastemaydogreatharmtothethingsaroundus.,3、原因状语从句：,通常由连词：because,as,since,nowthat引导。区别是:,because：表示“因为”，直接而明确的原因和理由，语气最强，why提问的句子，一般都用because回答。,Hedidntcomebecausehewasill.,since：表示“既然”，语气比because弱。,Sinceyouarehere,youmustdoit.,as：表示“因为”语气比because轻，引导从句可放主句前也可放主句后。,Youneedntgowithme,asyouarebusy.AsIwasafraid,Ihidmyself.,nowthat意思与since相似，表示“既然”。,NowthatyouareinHighSchool,youwillprobablyspendmoreinreading.Nowthatalltheguestshavearrived,letshaveourdinner.,注意：在强调句中强调原因状语从句，只能用because引导，不可用as或since，如：Itwasbecausehewasillthathedidntgowithus.,because可以引导表语从句,而as,since不可以，这时状语一般都是it,this,that,Itsbecauseheistoolazy.,for也表示“因为”，但是并列连词，它连接的不是状语从句，语气比较强。,Itmustbemorning,forthebirdsaresinging.,4、目的状语从句：,通常由that,sothat,inorderthat,sothat,lest,incase（以防、免得）等引导：,Hegotupearlyinorderthathecouldcatchtheearlybus.Shemarriedhimsothatshemighttendandcomforthim.Iexplainedagainandagainincaseheshouldmisunderstandme.,lest(以免，免得),forfearthatIhidthebooklest(=forfearthat)heshouldseeit.,目的状语从句中谓语动词常含有may(might),can(could)should,will等情态动词。,5、结果状语从句：,由that,sothat,sothat,suchthat引导：Itwasverycold,sothattheriverfroze.Thebookissowrittenthatitgivesaquitewrongideaofthefacts.Thereweresomanypeople(=suchalotofpeople)intheroomthatwecouldnotgetin.Hemadesuchanexcellentspeechthateveryoneadmiredhim.,6、条件状语从句:,由if,unless,aslongas(=solongas)(只要),incase(that)(如果，万一)等引导：,Ifplasticsandrubberareburned,theygiveoffpoisonousgases.,Unlessyouworkhard,youwillfail,Youcangoout,aslongas(solongas)youpromisetobebackbeforeeleven.,IncaseIforget,pleaseremindmeaboutthat.,注意：条件状语从句中的谓语动词的时态不可用将来时，只能用现在时态或过去时态表示将来时。,7、方式状语从句：,由连词：as,asif,asthough引导：Theteachertoldthestudentstodoashedid.Leaveitasitis.Heheardanoise,asifsomeonewasbreathing.Isawthemanlookingabouthimasifhewishedtoimpressuponhismindeverything.,asif和asthough意义和用法大致一样，引导的从句多用虚拟语气，但也可用陈述语气。HetreatsmeasifIwerehisownson.Hewalkedasifheweredrunk.,8、比较状语从句：,由连词asas,notso(as)as,than等引导：,Ihopeitwasasgoodastheoneyoulentme.Actuallytheoceanfloorarealmostasirregularastheexposedlandarea.,Noonecanbemorefitforhisofficethanheis.,Hecantrunsofastasshe.,注意：“the+比较级(接从句)，the+比较级(接主句)，这一句型也归在比较状语从句内。如：,Themoreyoustudy,themoreyouknow.Theharderwework,thehappierwefeel.,9、让步状语从句：,由though,although,as(虽然尽管),evenif,eventhough,wh-ever,nomatter-wh,whether引导.,whateverwhoeverwhicheverwheneverwhereverhowever,wh-ever,nomatterwhonomatterwhatnomatterwhichnomatterwhennomatterwherenomatterhow,nomatterwh-,Thoughheisold,yetheisactive.Althoughmostofthepeopleagreed,somewerenotwillingtoaccepted.Proudasthenoblesare,heisafraidtoseeme.Wewouldntloseheartevenifweshouldfailtentimes.,Whenever(=nomatterwhen)youcallonme,youarealwayswelcome.Wherever(nomatterwhere)youwork,youcanalwaysfindtimetostudy.Taketheoneyoulikebest,whichever(nomatterwhich)itis.,NomatterwhatIsayorhowIsayit,healwaysthinksImwrong.,Whetherhecomesornot,welldiscusstheproblemthisafternoon.,注意：（1）让步状语从句在句中的位置可放前也可放后，有时还可以插在主句中间，前置时，强调主句内容，后置时强调从句内容。,（2）though与although同义，用法基本一样，前者通俗，口语化；后者较正式，多放于句首，不能与but连用，但可以与yet,still等连用，用来加强语气。Though(Although)hewastired,yet(still)hewentonworking.,（3）as引导让步状语从句时从句部分语序要部分倒装。如：,Youngasheis,hecanreadandwriteinseveralforeignlanguage.（表语提前）,Childashewas,hehadtosupportthefamily.（表语名词提前并常省去冠词）Surroundedaswewerebytheenemy,wemanagedtomarchforward.（表语名词提前并常省去冠词）,状语从句的“简化”现象,一、当状语从句的主语是it,且谓语动词是be时,it和be要完全简化掉。If(itis)possible,hewillhelpyououtofthedifficulty.Youmustattendtheclassunless(itis)inconvenienttoyou.,二、当状语从句的主语和主句的主语一致时,从句可以将主语和be动词简化掉。,1.连词+形容词As(hewas)young,helearnedhowtorideabike.Whenever(sheis)free,sheoftengoesshopping.Workhardwhen