定语从句定义I. 定语从句起形容词的作用，在句中修饰一个名词或代词。被修饰的词叫做先行词，引导定语从句的词叫关系词，他的作用一是放在先行词与定语从句中间起了连接作用，二是在从句中担当一个成分，并与先行词保持数的一致。关系词先行词从句成分例句备注关系代词who人主语Do you know the man who is talking with your mother?whom, which和that在从句中做宾语时，常可以省略，但介词提前时后面关系代词不能省略，也不可以用thatwhom人宾语Mr. Smith is the person with whom I am workingThe boy (whom) she loved died in the war.whose人，物定语I like those books whose topics are about history.The boy whose father works abroad is my desk mate. tha
