一、在英文中，名词或名词短语主要充当四种成分，主语、宾语、表语和同位语。如果我们把句子当作名词来使用，分别在另一个句子中作主语、宾语、表语和同位语(见下表第二列)，于是就构成了四种从句：主语从句、宾语从句、表语从句和同位语从句。因为以为这四种从句在本质上相当于名词的作用，所以我们把他们统称为名词从句。请看例句：简单句名词从句“JaneEyre”isgreat.WhatIamreadingisgreat.Ibelievehiswords.Ibelievewhathesaid.Frenchisausefultool.ThisBMWiswhatIwant.Ilikethecar,Porsche.Themothermustacceptthefactthatherbabyisdeaf.二、三种句子来充当四种成分。(3，4)上面说到名词从句就是用一个完整句子充当另一个句子的某种句子成分便构成了具体某一名词从句。那么可以用什么样的句子来充当四种成分呢?答案是：陈述句Stuartisfat.一般疑问句Doesheeatmoreeveryday?特殊疑问句Howmuchdoesheeatathome?三、陈述句可分别充当四种句子成分(名词从句的重点内容)，要在陈述句首加上他that对于陈述句，我们要在句首加上that,然后把“that+陈述句”分别放在另一个句子的四种位置即构成四种名词从句。1.主语从句。“that+陈述句”在主语位置即成主语从句：Stuartisugly.ThatStuartisuglyisafact..ThatMalaysiansdon’tspeakgoodEnglishisobvious.更常见的是用it式主语置于句首，而将主语从句放在句末。例如：ItisafactthatStuartisugly.ItisobviousthatMalaysiansdon’tspeakgoodEnglish。因此下面都是常见的主语从句句型：(￥)①Itis+过去分词+that从句(found,believed,reported,thought,noted…)②Itis+形容词+that从句(clear,possible,likely,natural,certain,fortunate,necessary,strange…)③Itis+名词(短语)+that从句(apity,ashame,anhonor,agoodidea,amiracle…)2.宾语从句。“that+陈述句”在宾语位置即成宾语从句：Ithink(that)youturnedoffthelight.Weknow(that)womenloveshopping.Shebelieved(that)herchildwaspremature.只有宾语从句中的that才可以省去，其他名从that不省。3.表语从句。“that+陈述句”在表语位置即成表语从句：Myideaisthatthestudentsshouldbemoreopentoeachother.Thereasonisthathewascarelessandirresponsible.(考点)4.同位语从句。“that+陈述句”在同位语位置即成同位语从句：所谓同位语，就是用来补充说明名词的成分。TherumorthatTomwashedhissocksonceamonthturnedouttobeuntrue.Ourfathersbroughtforthuponthiscontinentanewnation,conceivedinlibertyanddedicatedtothepropositionthatallmenarecreatedequal.Asayinggoesthattomorrowisanotherday.四、一般疑问句可分别充当四种句子成分。1、一般疑问句语序变成陈述语序。2、用来whether或if引导。1.主语从句:doesshelovedog-walking?Whethershelovesdog-walkingornotisunknown.2.宾语从句:Idon’tknowif/whetherwhethershelovesdog-walking3.表语从句:Myconcerniswhetheryouareastudentornot.4.同位语从句:Theyarefacedwiththeproblemswhethertheyshouldcontinuetoplay.补充：ifwhether区别1)if一般用于引导宾语从句，而whether可引导所有名词从句Ifhecomesornotmakesnodifference.Thequestionisifhewillarrive.2)if不和ornot直接连用，一般不说ifornot。但可以说if…ornot。而whether没有此限制。Idon’tknowifornothearrives.Idon’tknowwhetherornothearrives.五、特殊疑问句可分别充当四种句子成分。特殊疑问句变成陈述句语序。Therearosethequestionwherewecouldgettheloan.Ihavenoideawhatgenderheis.Whyherefusedtocooperatewithusisstillamystery.Idon’tknowhowmanylettersIhavewrittentoher.NBAiswhatIamcrazyabout.HowChinashoulddevelopnextisaseriousproblem.Excuseme,canyoutellmewherethepostofficeis?Myquestioniswherewearegoingtohaveourholidays.Thepointiswhosebookisthemosthorrible.Whoevercomeswillbewelcomed.WhateverisleftoverisyoursDowhateveryouplease.Readwhicheverbooksyouplease.I'llg...