先行词:是在定语从句中,被定语从句所修饰的名词.例如:

　　HeisateacherwhoteachourEnglish.在这里定词从句whoteachourEnglish是来修饰前面的名词teacher.所以teacher就是一个先行词.

　　再说下它的用法：

　　1、先行词指人时,引导词可用Who,Whom,及that,其中当引导词在句中作主语时用Who或that；当其充当宾语时用whom或that,在非正式宾语中也可用who,也可省略.

　　aThatboywho/thatbrokethewindowiscalledTom.

　　bThepersontowhomyoujusttalkedisMrLi.

　　b句可改为：Theperson(that/whom/who)youjusttalkedtoisMrLi.

　　2、先行词指物时,引导词用that或which

　　a.Theyplantedthetreeswhichdidn’tneedmuchwater.

　　b.Thefish(which)weboughtwerenotfresh.

　　3、先行词指时间时,引导词用When/onwhich或inwhich

　　a.Istillrememberthedaywhen/onwhichIfirstcametoBeijing.

　　b.I'llneverforgettheyearwhen/onwhichweworkedonthefarm.

　　4、先行词指地点时,引导词用Where或inwhich

　　Thisisthehousewhere/inwhichwelivedlastyear.

　　或:Thisisthehousethat/whichwelivedinlastyear.

　　5、whose在定语从句中作定语时,可用来指人,也可以用来指物,如:

　　a.Thisistheboywhosemotherdiedamonthago.

　　b.Thisisthehousewhosewindowswerebroken.此句可改成：

　　Thisisthehousethewindouesofwhichwerebroken.

　　6、先行词表示原因时,引导词用why,如:

　　Thereasonwhyhewaslateforschoolwasthathehadbeenknockeddownbyabike.

　　二、物殊情况：

　　尽管有以上基本原则,但要学好定语从句更应注意以下特殊情况；

　　Ⅰ、当定语从句的先行词为表示人的不定代词,如anyone,anybody,everyone,everybody,noone,nobody,all,these,those等时,用who而不用that

　　Thosewhobreaktherulearepulished.

　　Anybodywhohadeyescouldseetheelephantwaslikeasnake.

　　Ⅱ.以who或which作主语的特殊疑问句中先行词指人,引导词只用That,如:

　　a.Whoisthepersonthatisstandingatthegate

　　b.WhichofyouthatknowssomethingaboutEnglishdoesn’tknowthisword?

　　Ⅲ、先行词指物时引导词用that而不用which的情况:

　　1、先行词有序数词或形容词最高级修饰时,

　　ThisisthebestcompositionthathasbeenwritteninEnglish.

　　2、先行词是all,something,anything,nothing,everything,little,few,much等不定代词时

　　Thereisnothing/little/muchthatwecandoforher.

　　3、先行词被all,every,no,some,any,little,much等修饰时

　　I’vereadallthebooksthatyougaveme.

　　4、先行词被theonly/very等修饰时

　　Thisisthevery/lastplacethattheyvisitedyesterday.

　　5、有两个以上先行词,分别表示人或物时

　　Theytalkedabouttheteachersandtheschoolsthattheyhadvisited.

　　6、先行词为基数时

　　YesterdayIcaughttwofish,Nowyoucanseethetwothatarestillaliveinabasinofwater.

　　Ⅳ.time为先行词时,前边如有序数词修饰时,定语从句引导词用that或什么也不用,如没序数词修饰时,用when或that均可

　　a.Thisisthelasttime(that)Ishallgiveyoualesson.

　　先行词指人时,引导词可用Who,Whom,及that,其中当引导词在句中作主语时用Who或that；当其充当宾语时用whom或that,在非正式宾语中也可用who,也可省略.

　　aThatboywho/thatbrokethewindowiscalledTom.

　　bThepersontowhomyoujusttalkedisMrLi.

　　b句可改为：Theperson(that/whom/who)youjusttalkedtoisMrLi.

　　2、先行词指物时,引导词用that或which

　　a.Theyplantedthetreeswhichdidn’tneedmuchwater.

　　b.Thefish(which)weboughtwerenotfresh.

　　3、先行词指时间时,引导词用When/onwhich或inwhich

　　a.Istillrememberthedaywhen/onwhichIfirstcametoBeijing.

　　b.I'llneverforgettheyearwhen/onwhichweworkedonthefarm.

　　4、先行词指地点时,引导词用Where或inwhich

　　This