that与which的用法区别两者都可指物，常可互换。
其区别主要在于：1.引导非限制性定语从句时，通常要用which：The current, which is very rapid, makes the river dangerous. 水流湍急，使这条河很危险。
He has to work on Sundays, which he doesn’t like. 他得在星期天工作，他是不喜欢这样的。
The London team, which played so well last season, has done badly this season. 伦敦队上一个季度打得很好，这个季度却打得很差。
2.直接放在介词后作宾语时，通常要用which：She may be late, in which case we ought to wait for her. 她可能晚到，那样我们就要等等她。
The documents for which they were searching have been recovered. 他们找寻的文件已找到了。
This morning some port wine came, for which I have to thank you. 今天早上送来一些波尔图葡萄酒，为此我得向你道谢。
注：有时“介词+which”引导的定语从句可以转换成“介词+which+不定式”结构：He had only the long nights in which he could study. =He had only the long nights in which to study. 他只有漫漫长夜可用来学习。
He had a couple of revolvers with which he could defend himself.= He had a couple of revolvers with which to defend himself. 他只有一两把手枪用来自卫。
3.当先行词是下列不定代词或被它们修饰时much, little, none, all, few, every(thing), any(thing), no(thing) 等时，通常用that：All that she lacked was training. 她缺的只是训练。
Have you everything that you need? 你需要的东西都有了吗?The sleeping man’s subconscious mind retained everything that was said around him. 这位酣睡的人头脑的下意识能记住他周围的人说的话。
She would never do anything that was not approved of by her parents. 她父母不赞同的事她绝不会做。
4.当先行词有the very, the only, the same 等修饰时，通常用that：This is the only example that I know. 我知道的例子只有这一个。
Those are the very words that he used. 那是他的原话。
5.当先行词有形容词最高级或序数词(包括last, next等)等修饰时，通常用that：This is the best dictionary that I’ve ever used. 这是我用过的最好的词典。
The first thing that you should do is to work out a plan. 你应该做的第一件事是订个计划。
6.当关系代词在定语从句中用作表语时，通常用that：China is not the country (that) it was. 中国已不是过去的中国了。
7.当先行词是一个既指人又指物的并列词组时，通常用that：They talked about the persons and things that most impressed them. 他们谈论了使他们印象最深的人和事。
8.当要避免重复时：Which is the course that we are to take? 我们选哪门课程？that与which的用法区别两者都可指物，常可互换。
其区别主要在于：1. 引导非限制性定语从句时，通常要用which：The current, which is very rapid, makes the river dangerous. 水流湍急，使这条河很危险。
He has to work on Sundays, which he doesn’t like. 他得在星期天工作，他是不喜欢这样的。
The London team, which played so well last season, has done badly this season. 伦敦队上一个季度打得很好，这个季度却打得很差。
2. 直接放在介词后作宾语时，通常要用which：She may be late, in which case we ought to wait for her. 她可能晚到，那样我们就要等等她。
The documents for which they were searching have been recovered. 他们找寻的文件已找到了。
This morning some port wine came, for which I have to thank you. 今天早上送来一些波尔图葡萄酒，为此我得向你道谢。
注：有时“介词+which”引导的定语从句可以转换成“介词+which+不定式”结构：He had only the long nights in which he could study. =He had only the long nig hts in which to study. 他只有漫漫长夜可用来学习。
He had a couple of revolvers with which he could defend himself.= He had a co uple of revolvers with which to defend himself. 他只有一两把手枪用来自卫。
3. 当先行词是下列不定代词或被它们修饰时much, little, none, all, few, every(thing), any(thing), no(thing) 等时，通常用that：All that she lacked was training. 她缺的只是训练。
Have you everything that you need? 你需要的东西都有了吗?The sleeping man’s subconscious mind retained everything that was said around him. 这位酣睡的人头脑的下意识能记住他周围的人说的话。
She would never do anything that was not approved of by her parents. 她父母不赞同的事她绝不会做。
4. 当先行词有the very, the only, the same 等修饰时，通常用that：This is the only example that I know. 我知道的例子只有这一个。
Those are the very words that he used. 那是他的原话。
5. 当先行词有形容词最高级或序数词(包括last, next等)等修饰时，通常用that：This is the best dictionary that I’ve ever used. 这是我用过的最好的词典。
The first thing that you should do is to work out a plan. 你应该做的第一件事是订个计划。
6. 当关系代词在定语从句中用作表语时，通常用that：China is not the country (that) it was. 中国已不是过去的中国了。
7. 当先行词是一个既指人又指物的并列词组时，通常用that：They talked about the persons and things that most impressed them. 他们谈论了使他们印象最深的人和事。
8. 当要避免重复时：Which is the course that we are to take? 我们选哪门课程？From: /grammar/dingyu/2011-07-15/149311.htmlthat和which做比较，主要在于它们在定语从句中的用法that 和which在定语从句中都是做关系代词，指代先行词是事物的名词或代词（that还可以指代人，which 不可以）。
通常情况下二者可以互换。
区别：关系代词用that（不用which）的情况：1. 先行词是all, anything, everything, nothing等,关系代词应用thatThat's all that he told me.2.先行词前有the only, the same, the very 或no, little, much,any, every, all 等修饰时,关系代词应用thatShe is the only person that I know in this company.3. 先行词前有序数词或形容词最高级修饰时,关系代词常用that The first thing that I want to do is to take it away.4. 当先行词同时含有"人"或"物"时,关系代词应用that5. 在固定结构the same...that...; so...that...; such...that...以及it is/was...that...的强调句型中,要用thatThis is the same park that we once visited.6. 如主句以there be开头时,关系代词应用thatThere is a room that has two windows.关系代词用which（不用that）的情况：1. 非限制性定语从句中关系代词一般要用whichShe won the competition, which made the whole family very happy.2. 关系代词前如有介词,关系代词须用which; 如把介词移至句末,可用that(或省略)There’s only one problem about which they disagree.This is the key (that) she was looking for.3. 如果先行词是that,关系代词应用whichI know that which you told me.4. 如先行词和定语从句之间被其它较长的成分分隔,常用which Larry told her the story of the young airman which I narrated atthe beginning of this book. (先行词为story)5. 在"those+复数形式的名词"结构中,其后的关系代词多用whichA shop should keep a stock of those goods which sell best.6. 一个句子中如有两个定语从句,第一个定语从句用了关系代词that,第二个从句中的关系代词宜用which;但在平行结构中,应重复同一个关系代词This is the book that you bought which you have lost.I have a house which is located on the hillside, which faces the south.此外，that还可引导同位语从句,which不能I have heard the news that they had won the game.。