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英语三大从句主语从句用作主语，如：：Thattheearthisroundistrue.地球为圆的是真实的。宾语从句用作宾语。如：Doyouknowwherehelives?表语从句用作表语，如：Myopinionisthatyoushouldnotgoalone.我的意见是你不应单独前往。同位语从句用于解释说明前面的名词。如：Thefactthattheearthisroundistrue.地球是圆的的事实是真实的。（that从句用于解释说明thefact）定语从句相当于一个形容词，用于修饰前面的名词。如：ThestudentwhoansweredthequestionwasJohn.回答问题的学生是John.状语从句相当于一个副词，如：Whenitrains,Iusuallygotoschoolbybus.天下雨时，我通常坐公共汽车上学。（时间状语）Ifhecomestomorrow,youwillseehim.如果他明天来，你就可以看见他。（if引导的条件状语从句，其结构为：if+状语从句，＋主句）。要注意在状语从句中有一个规则是“主将从现”，即主句是将来时，则从句要用一般现在时表示将来。主句和从句的划分方法是相同的。句子的成分从谓语动词处来划分比较容易。谓语动词前面的部分是主语，后面常接宾语，修饰谓语动词的是状语，修饰主语、宾语的是定语，若谓语是系动词，则系动词后的部分是表语。如：Iamateacher.其中，I是主语，am是谓语，ateacher是表语。Helikesplayingfootballverymucy.其中，he是主语，likes是谓语，playingfootball是宾语，verymuch是状语。名词性从句名词性从句有四类：宾语从句、主语从句、表语从句、同位语从句。例如：宾语从句：Idon’tknowwherehewillgo.主语从句：Wherehewillgoisunknown.表语从句：Theproblemishowwecangetsomuchmoney.同位语从句：Weallfeelsorryaboutthenewsthathefailedinthegame.下面几点是学习名词从句要加以注意的：1．whether和if都可以引导宾语从句表达“是否”意，（即引导宾语从句时if和whether可以互换）但以下几种名词从句要用whether（不用if）引导：（1）引导主语从句，且在句首时。例：Whetherhehaswonthetennisisnotknown.(但Itisnotknownwhether/ifhehaswonthetennis).（2）引导表语从句时。例Theproblemiswhetherhecangetajob.（3）引导同位语从句时。例：Ihavenoideawhetherhewillcome.（4）介词后的whether从句。例：IworryaboutwhetherIhurtherfeelings.2．位于句首引导主语从句的that不可忘。例如：Thathegotthefirstplaceinthecompetitionsurprisedallofus.3．在“Itissuggested/proposed/ordered/apity/nowonder/necessary/strange/…＋that从句”结构中，that从句谓语有时用（should）do这样的虚拟语气形式。例如：Itissuggestedthatwe(should)improvetherelationsbetweenus.Itisapitythatone(should)stayinoneplaceallone´slife.Itisstrangethatsheshouldhavefailedtoseeherownshortcomings（缺点）.4．在“Thereasonwhy…isthat…”句式中that不要误为because.例如：Thereasonwhyhedidn´tgotoschoolyesterdayisthathewasill.5．名词从句中that,what用法比较：引导名词从句的that是连词，在句中无成份，无意义，而what是连接代词，what＝thething(s)that.例如：Itwastoldinyesterday´snewspaperthatwhatthestudentshaddonewaspraisedbythefactory.Iknowthathewillstudy.Iknowwhathewillstudy.Thatheworkshardathislessonsisknowntousall.Whatheworkshardatisknowntousall.AllIaskisthatyoushouldtellthetruth./Heisnotwhat(＝thepersonthat)heusedtobe.他和以前大不相同了。6．where在名词从句中的使用特点：where在名词从句中有时可以变为“theplacewhere”,有时可以变为“介词＋theplacewhere”形式。例如：主从：Where(＝Theplacewhere)shehasgoneisstillunknown.宾从：Wouldyoupleasetellmewhere(＝theplacewhere)MrSmithlives?表从：Yourdictionaryremainswhere(＝in/attheplacewhere)youput.同位从：Haveyouanyideawhere(＝oftheplacewhere)sheisspendingherholidays?7．无论是哪种名词从句都是陈述语序。例如：Iknowwherehelives./Pleasetellmewhathernameis.当一个特殊疑问句本身就是陈述语序（即“主＋谓＋（宾）”或“主＋系＋表”结构），将其变为间接引语（即宾语从句）时，无需改变语序。例如：What´sthematterwithhim?Sheaskedmewhatwasthematterwithhim.Wholooksafteryourgrandfather?Heaskedmewholookedaftermygrandfather.形容词性从句定语从句一、定语从句与引导词定语从句是在复合句中修饰某一名词或代词的从句。被修饰的名词或代词叫做选行词，而引导定语从句的词叫引导词，有关系代词和关系副词两类。懂得什么样的先行词后用什么样的引导词是学好定语从句的关键。1．关系代词有：that,which,who,whom,whose,在定语从句中作主语、宾语中表语，whose作定语。代人的有：who,whom,whose,that；代物的有：that,which,whose.例如：ThemanwhohelpedyouisMrWhite.(who代人，在定语从句中作主语)Thatistheperson(whom/who/that)youwanttosee.(whom,who,that代人，在定语从句中作宾语，可省略)I´mnotthefool(that)youthoughtmetobe.(that代人，在定从中作表语)Adictionaryisausefulbookwhich(＝that)tellsusthemeaningofwords(which或that代物，在定从中作主语)2．关系副词有：when(指时间)，where(指地点),why(指原因)，在定语从句中作状语。例如：Wouldyousuggestatime(when)wecanhaveatalk?(when可省略)Thehousewheretheyliveisnotverylarge./Thisisthereasonwhyhedidnotcametothemeeting.注意：不是表时间的先行词都用when引导定从，不是表地点的先行词都用where引导定从。例如：We´llvisitthefactorywhich(＝that)makesradios.(which或that在定从中作主语，where不可用主语，故不可用)Theystillrememberthehappydays(which/that)theyspentinBeidaihe.(which或that在定从中作spent的宾语，when不可作宾语，故不可用)二、限制性定语从句与非限制性定语从句限制性定语从句和主句之间不用逗号分开，修饰主句中的某一个名词或名词词组或代词；非限制性定语从句常用逗号和主句隔开，可以修饰主句中的某一个词，也可修饰整个句子。非限制性定语从句不能用that引导，引导非限制性定语从句的关系词不能省略。非限制性定语从句例：LiPing´sfather,whoworksinafactory,isanengineer./Hetoreupmyphoto,whichmademeveryangry.(which指代主句内容，因前后两句是因果关系，此时which不可换为as。)Heisgoodatphysics,asisknowntousall.＝Asisknowntousall,heisgoodatphysics.(as指代主句内容，在asisknown/believed,asweallknow/believe这类结构中as不可换为which)三、只用that引导和不用that引导的场合1．只用that引导和不用that引导的场合1）当先行词既包括人又包括物时：Hetalkedaboutthemenandthebooksthatattractedhim.2）指物的先行词被any,every,only,very,all,no等修饰时：Thesearetheverypointsthatinterestme./That´stheonlywatchthatIlikemost.3）指物的先行词被序数词或形容词最高级修饰时：Thefirststepthatwearetotakeisverydifficult./Thisisthesecondcardthathegaveme.4）先行词是指物的不定代词all,little,few,much,及everything,anything,nothing等时：Thereisstillmuchthatcanbedoneaboutit./Haveyougoteverythingthatyouneed?5）先行词是who时：Whothathaveseenhimdoesnotlikehim?2．不用that的场合如下：1）非限制性定语从句中Lastnight,Isawaverygoodfilm,whichwasabouttheLongMarch.2）介词放在关系代词之前时ThisisthemanfromwhomIlearntthenews3）句中出现了that，或先行词是that时IhavefoundthatwhichIwaslookingfor.副词性从句状语从句时间状语从句：WhenSusangoestotown,shewillvisithergrandma..苏珊每次进程，总要去看望她奶奶。地点状语从句：IwillgowhereIamneeded.哪里需要我，我就到哪里去。方式状语从句：Ihavechangeditasyousuggest.我已经按照你的建议作了改变。原因状语从句：Marydidn’tgoshoppingbecauseIadvisedhernotto.玛丽没有去购物，因为我劝她不要去。目的状语从句：Theyworkedhardinorderthattheymightsucceed.他们努力工作，以便能够获得成功。结果状语从句：Wastemustbetreatedsothatitdoesnotbecomeadangertolife.废物必须进行处理，这样它才不会成为危害生命的东西。条件状语从句：Ifhewor