扁管铝型材:定语从句中，关系词that,which.who的用法有什么不同？

关系词that,which.who的用法、区别：）~
定义(Definition):在一个复合句中,修饰某一名词或代词的从句叫做定语从句.这个被修饰的词就叫先行词引导定语从句的词有关系代词that, which, who(宾格whom,所有格whose),as和关系副词where,when,why.

1 由关系代词引导的定语从句
A plane is a machine that can fly. (作主语)
that 指物 The noodles (that) I cooked were delicious. (作宾语)

总结:(1)当that和which作主语时不能省略;作宾语时,在非正式文体中通常可以省略;whom也可以省略,但当whom位于介词后面时,不能省略.注意:在定语从句中,有的成分可以省略,但是主句中的先行词一定不能省略,如果一个定语从句在主句中缺少先行词,则一定要补上先行词.

(2) 关系代词whom, which (没有that) 在从句中作宾语时,可以和介词一起放在先行词和从句之间,构成介词+关系代词 引导定语从句,也可放在从句中相关动词的后面(含介词的动词短语).如:The man to whom you talked is a famous runner. = The man (whom) you talked to is a famous runner. 但是有的含有介词的动词短语一般不宜拆开(因为只有当它们连在一起的时候才有意思,拆开后意思就变了.

(3)引导词只能用that的情况
* 先行词既有人又有物时,要用that 而不用which/who引导定语从句. He talked about some writers and books that were unknown to us all.
* who或者which开头的疑问句中,若还要用关系代词引导定语从句时,要用that引导定语从句而不用who和which.Who is the girl that is singing in the hall (避免重复)
* 在there be 句型中,只用that,不用which. There is a park (that) we often visit on Sundays.
* 当先行词在定语从句中充当表语时,关系代词一般只能用that.My hometown is no longer the town (that) it used to be ten years ago.
(4) 引导词不能用that 的情况
* 非限制性定语从句中不能用that.
* 介词后不能用that.
* 当关系词后面有插入语时用which引导定语从句而不用that. Here is the English grammar book which, as I have told you, will help to improve your English.
* 先行词本身是that时,一般用which引导定语从句,以避免重复.The predicate is that which is said of the subject.

that只能用在限定性定语从句，与which用法基本相同。which用于先行词为物的句子中，who是用于先行词为人的句子中。