定语从句的先行词在从句中做一定成分 .而同位语从句前面的那个名词 在从句中不作任何成分 .如:The news that he told me surprised me.(这是定语从句,先行词news 在从句中做told 的宾语) The news that he went abroad surprised me (这是同位语从句,名词news 在从句中没有做任何成分.) 同位语代替前面的名词时,有两种情况:1.用不定代词 the one,one,the ones,ones,或those. 如:He is a strict scientist,one who put his heart on the his field. 2.用一个名词,进一步解释前面的名词.如:John is honest,a man who has never lied.