关系代词that与which都可以引导定语从句，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，但是它们的用法是有区别的，英语语法网的小编总结了以下三点主要的区别。
第一、which可引导非限制性定语从句，that则不能
He had failed in the maths exam，which made his father very angry.
他数学考试没有及格，这使他的父亲很生气
第二、which之前可以有介词，that之前则不能有介词
That is the house in which Lu Xun used to live.
这就是鲁迅过去居住的房子
第三、that和which都指物时，在以下4种情况下，用that而不能用which
1、当先行词是all，everything，nothing，something，anything，much，little，few等不定代词时
There is nothing that can prevent him from doing it.
没有什么能阻止他不干那件事
That is all that I want to say
那就是我想要说的
2、当先行词被序数词修饰时，用that
The first place that they visited in Guilin was Elephant Trunk Hill.
在桂林他们所参观的第一个地方是象鼻山
3、先行词被形容词最高级修饰时，用that
This is the best film that I have ever seen.
这部电影是我看过的最好的一部
4、先行词被the very，the only，the just等修饰时，用that
This is the very dictionary that I want to buy.
这正是我要买的词典
Mr Smith is the only foreigner that he knows.
史密斯先生是他认识的唯一的外国人
5、在those后面的定语从句常用which指物，用who指人，而不用that
I gave him those books which he liked most.
我把他最喜欢的书给了他