1. 关系代词who指人，在从句中作主语；whom指人，在从句中作宾语，在限制性定语从句中常常省略；whose指人，作定语；which指物，在从句中作主语或宾语，作宾语时常可省略；that可指物或人，在从句中可作主语或宾语，指物时用法和which大致一样。
（1）which 作主语。
1) Take the pencil which is lying on the desk.
把课桌上的那支铅笔拿去。
We visited the Jade Buddha Temple, which is in the northwestern part of Shanghai.
我们参观了玉佛寺，它在上海西北边。
（2）which作宾语。例如：
1) That is the house in which Mr. Wang lives.
这就是王先生住的房子。
2) This is the novel which Mr. Zhang mentioned this morning.?
这就是今早王先生提到的那本书。
（3）that的用法。
(注意它在限制性定语从句中可指物也可指人，但不能作从句中的介词宾语)
Could you lend me the novel about which you were talking the other day?
你能把那天你们讨论的那本小说借我吗?
All that glitters is not gold.
不是所有发光的东西都是金子。
2. 关系副词when，where，why在从句中均作时间状语、地点状语和原因状语状语。
This is the workshop where (=in which) I work.
这是我工作的车间。
He came at a time when we needed help.
他在我们需要人帮忙的时候来到了。
The reason (why) he changed his mind is not clear.
他改变主意的原因尚不清楚。
3. whom，which在定语从句中充当介宾时，介词的位置一般来讲，如果是含有介词的短语动词，介词仍要在动词之后，而which，whom的位置不变，但如果介词短语独立于从句谓语动词之外，这时介词应置于which，whom之前。例如：
The writer wrote lots of operas, the most famous of which is Carmen.
这位作家写了很多戏剧，其中最著名的就是卡门。?
This rule is out of date. It is the thing which the government should do away with.
这条规矩已经过时了。政府应该把它废除了。
4. 关系代词who，that亦可用作现在或过去分词的宾语(who指人，that指物或人)，但分词必须放在从句之末，而who在非正式文体中可省略。
5. 关系代词which的特殊用法。
which的先行词有时不是一个单词，而是前面整个主句或主句的一部分所表达的概念，which在这时意同 and this。例如：
They have invited me to take part in the party, which is very kind of them.
他们很客气，邀请我们参加聚会。
The worker didn't do any work，which made his boss very angry.
那个工人什么活也没干，这令老板非常生气。
6. ?that和which均指物时，一般没什么区别，但在一些特殊情况下不可混用。
如在下列情况下，一般须用that。
（l）先行词是all，everything，nothing，something，anything， little等不定代词。例如：
All that you have to do is to make a clear copy of the draft.
你要做的就是弄出一份草稿的清晰附件。
Everything that the teacher said seemed quite reasonable if you had mastered the main meaning of his words.
如果你抓住了老师话的主旨，其实都很有道理。
（2）先行词为形容词最高级序数词修饰时(that也可省)。例如：
This is the first thing that I want to say.
这是我首先要说的事。
2) This is the best step that can be taken.
这是能采用的最好的措施。
（3）还有以“as”引起的定语从句，多和such连用。例如：
Such people as described in the novel are rare nowadays.
这本小说中描述的人在当下很少了。
Hearing the news that her husband got a heavy sentence, she left with a weight on her mind such as she had never had before.
听到丈夫判了重刑，她拖着从没有过的沉重的头走了。
She opposed our idea, as could expected.
她反对我们的看法，就像预料的那样。