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英语三大类从句之用法与比较从句概述•从句只能做主句的某一部分,依附于主句而存在,不能独立。•从句也具有句子的特征，即有自己的主谓结构；而且带有引导词。•根据从句在句中的作用，可分为名词性从句、形容词性（定语）从句和副词性（状语）从句三类。一、名词性从句名词性从句包括主语从句、宾语从句、表语从句和同位语从句。其关联词有连词that,if,whether；连接代词what,who,which和连接副词when,where,why,how等。从句连接词主语从句宾语从句介词后宾语从句形容词后宾语从句表语从句同位语从句thatwhetherifWh-词（含how)带后缀－ever的词连接词的用法(一)1.that连词that本身无实际意义，在从句中不担当任何成分，在宾语从句中有时可以省略。如：Ihear(that)hehasjoinedthefootballclub.Thatlighttravelsinastraightlineisknowntoall.Isitcertainthattheywillwin?为保持句子平衡，that引导主语从句时，常用it作形式主语而把真正的主语从句后置。主要有以下几种情况：①Itis+n.(apity/ashame/afact/nowonder,etc)+that-clauseItisafactthatEnglishisbeingacceptedasaninternationallanguage.Itisnowonderthatheisnothungry;hehasbeeneatingsweetsallday.②Itis+adj.(certain/likely/probable/true,etc.)+that-clauseItisprobablethathetoldhereverything.Itistruethatthescientistwillgiveusalecturenextweek.③Itis+p.p.(said/reported/believed,etc.)+that-clauseItisreportedthatChinahassentanotherman-madesatelliteintoorbit.④It+v.(seems/happened,etc.)+that-clauseItseemsthatAliceisnotcomingtothepartyatall.IthappenedthatIwasoutthatday.⑤其他情况:Itdoesn’tmatterwhetherhewillcomeornot.Itmakesnodifferencewherewehadthemeeting.Itsuddenlyoccurredtomethatshehadforgottentolockthedoor.连接词的用法(二)2.whether和if连词whether和if表“是否”之意，在从句中不可省略。在下列情况中只用whether不用if:⑴引导主语从句、表语从句和同位语从句时；Thequestioniswhetheritisworthtrying.Whethershecomesornotmakesnodifference.IhavenoideawhetherIshouldbelievehimornot.⑵从句作介词的宾语时；Ryanwasworryingaboutwhetherhehadhurtherfeelings.⑶ornot紧随其后时；Idon’tcarewhetherornothehasaholiday.⑷后接不定式时。Shecan’tdecidewhethertogo.３．Who,whom,whose,what,which连接代词Who,whom,whose,what,which等在从句中既起连接作用，又担当主语、宾语、表语等成分，并保留其特殊疑问词词义。如：Nooneknowswhohewaswaitingfor.Tellmewhosehouseitis.Letmeknowwhichtrainyouwillbearrivingon.连接词的用法(三)连接词的用法(四)４．where,when,why,how连接副词where,when,why,how等在从句中作状语，其词义与特殊疑问词词义相同。Idon’tknowwherewearegoingtohavethemeeting.Shealwaysthinksofhowshecanworkwell.WhatI’manxioustoknowiswhenwecanvisitthemuseum.Pleasetellmewhenyouwillarrive.连接词的用法(五)5.whoever,whomever,whatever,whichever,whosever连接代词whoever=anyonewho,whomever=anyonewhom,whatever=anythingthat,whichever=anythingthat.如：Whoevercomestotheclubiswelcome.Whateverisworthdoingatallisworthdoingwell.Youmaydowhateveryouwill.Whoseverbookisoverduewillbefined.Youmayofferthebooktowhoeverwantsit.Youmayofferthebooktowhomeveryoulike.二、定语从句•在复合句中，修饰主句的某个名词或代词，或修饰整个主句的从句，叫做定语从句。被定语从句修饰的词叫先行词，定语从句位于先行词之后。定语从句一般由关系代词和关系副词等引出。关系代词who,whom,whose,which,that,as和关系副词when,where,why须位于从句之首、先行词之后。起着连接先行词和定语从句的作用，同时又在定语从句中充当某一成分。关系代词who,whom,whose,which,that,as在定语从句中作主语、宾语或表语。关系副词when,where,why在定语从句中作状语。限制性定语从句和非限制性定语从句⑴限制性定语从句起修饰、限定或确定的作用，同先行词的关系十分密切，是先行词不可缺少的定语。如果将从句去掉，主句的意思就不完整，甚至不合乎逻辑。常翻译成带“的”字的定语性词组。如：Theboyswhoareplantingtreesonthehillaremiddleschoolstudents.在山上种树的男孩都是中学生。⑵非限制性定语从句跟先行词的关系不密切，它只是对先行词起附加说明作用。如果将其去掉，主句的意义仍然完整并合乎逻辑。从句和主句之间用逗号隔开。常翻译成并列分句。如：Tom’sfather,whoisoversixty,stillworksharddayandnight.汤姆的父亲已年过六旬，依然努力工作着。关系代词的用法（一）⑴who指人，是主格，在从句中作主语。如：Doyouknowtheboywhoisstandingunderthetree?HeisoneofthestudentswhohavebeentoBeijing.HeistheonlyoneofthestudentswhohasbeentoBeijing.注：关系代词在从句中作主语时，其人称和数要与其先行词一致。⑵whom指人，是宾格，在从句中作宾语．如：Thestudentwho(whom)wevisitedyesterdayisafamousartist.注：who在口语中可代替whom。关系代词在从句中作宾语时，一般可省去。⑶whose是所有格，多指人，也可以指物．指物时可与ofwhich换用。MrsWangislookingafterthelittlechildwhoseparentshavegonetoShanghai.Helivesinthehousewhose(thewindowsofwhich)facesthesouth．关系代词的用法（二）⑷which指物，在定语从句中可作主语或宾语。Helikestousethedictionarywhichwaspublishedin1986.注：关系代词作介词宾语时，介词可置于关系代词之前或之后。介词前置时，关系代词不可省。指人时亦不可用who代替whom。如：Thisisthehouseinwhichwelivedlastyear.Thisisthehouse(which)welivedinlastyear.注：短语动词中的介词不可与动词拆开；在定语从句中，其介词不可前置Isthisthebooksheislookingfor?关系代词的用法（三）⑸that指人或物，在定语从句中可作主语或宾语。代替who,whom或which。但that在定语从句中可作介词的宾语时，介词不可前置。如：Thegirl(that/who/whom)ourteacherisspeakingtoisourmonitor.⑹as作为关系代词引导限制性定语从句时，常用在such,thesame之后。Suchstampsas(Stampssuchas)youhavecollectedareveryvaluable.ThisisthesamepenasIusedyesterday.c.f.ThisisthesamepenthatIusedyesterday定语从句只用that不用which的几种情况that指物时一般可以和which换用，但在下列几种情况下只用that不用which：①先行词为all,anything,everything,nothing,something等；如:Wearereadytodosomethingthatisofsomehelptoothers.②先行词被all,only,no,some,any,every,each,few,little等修饰时；如：Ihavereadallthebooks(that)yougaveme.③先行词被序数词或形容词最高级等修饰时；如：Thefirstlesson(that)MrGreengaveuswillneverbeforgotten.④如果有两个或两个以上分别表示人和物的先行词时；如：Weknownothingaboutthedoctorsandhospitals(that)youaretalkingabout.⑤当主句是以who或which开头的疑问句时;如Whoisthatboythatwasherejustnow?⑥当引导词在从句中作表语时。如；Chinaisn’tthecountrythatitusedtobe.定语从句不能使用that的情况１定语从句中介词置于关系代词之前时，指人用whom，指物用which。如：•Doyouknowthemantowhomheisspeaking?•ThisisthehouseinwhichIlivedlastyear.２引导非限制性定语从句不能用that。如：•MrSmithhastwosons,bothofwhomworkedabroad.•Beijing,whichisthecapitalofourcountry,haschangedalot.•Theyarrivedatafarmhouse,infrontofwhichsataboyofseventeen.which与as引导的非限制性定语从句which与as均能引导非限制性定语从句，区别在于：⑴which引导非限制性定语从句可以修饰某个先行词，也可以修饰整个主句；as引导的非限制性定语从句则揭示整个主句的内容。Thenewcar,whichIpaidseveralthousandpoundsfor,isnotrunningwell.Theyrelyonthemselves,whichismuchbetter.⑵as表示说话人对话语的看法、态度、依据、解释或评论；whi