定语从句及相关术语
1.定语从句：定语从句是由关系代词或关系副词引导的从句,其作用是作定语修饰主句的某个名词性成分,相当于形容词,所以又称为形容词性从句,一般紧跟在它所修饰的先行词后面.
2.关系词：引导定语从句的关联词称为关系词,关系词有关系代词和关系副词.关系代词有that, which, who, whom, whose, as等；关系副词有where, when, why等.关系词常有3个作用：1,引导定语从句.2,代替先行词.3,在定语从句中担当一个成分.
注：关系代词有主语.宾语之分.一般whom作为宾语.
3.定语：定语用来限定、修饰名词或代词的,是对名词或代词起修饰、限定作用的词、短语或句子,汉语中常用‘……的’表示.主要由形容词担任.此外,名词,代词,数词,分词,副词,不定式以及介词短语也可以来担任,也可以由一个句子来担任．单词作定语时通常放在它所修饰的词之前,作前置定语.短语和从句作定语时则放在所修饰的词之后,作后置定语.
4、先行词：被定语从句修饰的名词、代词称为先行词.
关系代词引导的定语从句举例
关系代词所代替的先行词是人或物的名词或代词,并在句中充当主语、宾语、定语等成分.关系代词在定语从句中作主语时,从句谓语动词的人称和数要和先行词保持一致.
1、who, whom, that
这些词代替的先行词是人的名词或代词,在从句中所起作用如下：
(1) Is he the man who/that wants to see you? 他就是想见你的人吗?（who/that在从句中作主语）
(2) He is the man whom/ that I saw yesterday. 他就是我昨天见的那个人.（whom/that在从句中作宾语）
2、Whose 用来指人或物,(只用作定语, 若指物,它还可以同of which互换）
(1) They rushed over to help the man whose car had broken down. 那人车坏了,大家都跑过去帮忙.
(2) Please pass me the book whose (of which) cover is green. 请递给我那本绿皮的书.
3、 which, that 它们所代替的先行词是事物的名词或代词,在从句中可作主语、宾语等,例如：
(1) A prosperity which / that had never been seen before appears in the countryside. 农村出现了前所未有的繁荣.（which / that在句中作主语）
(2) The package (which / that) you are carrying is about to come unwrapped. 你拿的包快散了.(which / that在句中作宾语）