定语从句概要：（这是有关定语从句的精要介绍,涵盖了有关定语从句的各个方面,供参考：）引导定语从句的关联词包括关系代词和关系副词.关系代词有that,which,whose,who,whom,as；关系副词有when,where,why.关系代词和关系副词在定语从句中都充当一定的句法成份.关系代词在从句中充当动词的宾语时一般可以省略.关系代词的选用比较复杂,受下列条件的制约：(1)要看先行词是指人还是指物,(2)要看关系代词在从句中句法功能,(3)要看定语从句是限定性的还是非限定性的.在定语从句中充当的成分↓用于限定性或非限定性从句只用于限定性从句指人指物指人或指物主语whowhichthat宾语whomwhichthat谓语whosewhose(ofwhich)That只能用在限定性定语从句中,而who,whom,which,which既可用于限定性定语从句中,也可用于非限定性定语从句.Iknowthatheisamanwhomeanswhathesays.Iknowthatheisamanthatmeanswhathesays.【我知道他是一个守信用的人.】Thegentlemanwhomshemetaddressedherwithcourtesy.Thegentlemanthatshemetaddressedherwithcourtesy.【她遇到的那位先生很有礼貌地向她打了招呼.】Thegentlemanshemetaddressedherwithcourtesy.（在从句中充当动词宾语的关系代词,可以省略.）Thewatchwhichwaslosthasbeenfound.Thewatchthatwaslosthasbeenfound.【丢了的表找到了.】Hereisthematerialwhichyouneed.(注：现代美语中不允许这样用)Hereisthematerialthatyouneed.Hereisthematerialyouneed.【你要的材料在这儿了.】Youaretheonlyonewhoseadvicehemightlistento.他也就是听你的话吧.关系副词的选用相对来说比较简单,如果先行词是表示时间的名词,如time,day等,则用when,如先行词为表示地点的名词,如place,house,area等等,则选用where.如果先行词为reason则选用whyIwillneverforgetthemountainvillagewhereIspentmychildhood.IwillneverforgetthemountainvillageinwhichIspentmychildhood.我永远也不会忘记我度过童年的那个小山村.Idon’tknowthereasonwhyhedidthat.Idon’tknowthereasonforwhichhedidthat.【我不知道他为什么这么做.】当先行词是all,something,nothing等不定代词时,或者先行词的前面有first,last,only,few,much,some,any,no等词修饰时,或者先行词的前面有最高级修饰时,一般只用that而不用which来引导定语从句：IhaveexplainedeverythingthatIcantoyou.IhaveexplainedeverythingIcantoyou.【我已经尽一切可能把事情向你解释得一清二楚.】具体详情请上百度百科查询.从句—请点击此连接就可查询各种从句的具体解释http://baike.baidu.com/view/138129.htm