定语从句中,引导词如果是非谓语动词时,引导词可省略,如果非谓语动与先行词表主动用doing,被动用done,将来用todo或者将来的被动用tobedone,引导词介词宾语时,先行词与介词宾语不能省略.

　　例如：

　　Theman(whoistalking)withmymotherismyteacher.=Theman(talking)withmymotherismyteacher.

　　Thisisourschool(whichwasbuilt)tenyearsago.=Thisisourschool(built)tenyearsago.

　　Thisistheworkwhichwilbefinishedinanhour.=Thisistheworktobefinishedinanhour.

　　I'mthepersonwhowillaskyouaquestion.=I'mthepersontoaskyouaquestion.

　　当介词在定语从句的后半部分是,作宾语的关系代词可省,当介词紧跟在先行词后是关系代词不可省；如：

　　MissLiistheperson(whom)mymotheristalkingwith.句中whom可以省略.

　　=MissLiisthepersonwithwhommymotheristalkingwith.句中whom不可以省略.