在复合句中修饰名词或代词的从句叫定语从句。被修饰的名词或代词叫先行词。引导定语从句的关系代词有who ,whom ,whose ,which ,that等和关系副词where ,when ,why等。关系代词和关系副词在定语从句中担任句子成分。1 .who在从句中作主语 (指人 )。Hewasthethiefwhostolemynec The clause that modifies a noun or pronoun in a compound sentence is called an attributive clause. The modified noun or pronoun is called an antecedent. The relative pronouns of the guide attributive clauses are who, whom, whos, which, that, etc. and the adverbs where where, when, why and so on. Relational pronouns and relational adverbs serve as sentence components in attributive clauses. 1 .who is the subject (a person) in a clause. Hewasthethiefwhostolemynec