关系代词：
　　who，which，that作从句的主语
　　whom，which，that作从句的宾语(可省略)
　　whose从句中作定语
　　以下情况只能用that，不能用which:
　　i. 先行词为不定代词all, little, none，any，every，no，much, anything, nothing
　　ii. 先行词有最高级和序数词修饰时(包括: the only, the very, the same, the last, the next等)
　　iii. 先行词既有人又有物的时候
　　以下情况只能用which，不能用that;
　　① 引导非限制性定语从句(包括代表整个主句的意思时)
　　② 介词+关系代词的结构中
　　关系副词：
　　when指时间，在定语从句中作时间状语
　　where指地点，在定语从句中作地点状语
　　why指原因，在定语从句中作原因状语，只修饰reason。
　　如果用定语从句把两个句子合二为一:首先找出两个句子当中相同的部分，定语从句修饰的就是这一部分。要把其中一个句子变成定语从句，就要把这句中相同的那个部分用一个关系词来代替;代替时，先看被代替的部分是指人还是指物、再看它作什么句成分。指人并作主语的，就用who。或that;指人并作宾语的，就用whom或that;指人并作定语的，就用whose。指物并作主语的，就用which或that认指物并作宾语的，还是用which或that认是物并作定语的，就用whose或of which。这样找好并替换以后，再把这个关系代词放到要变成定语从句的那个句子的最前面(被代替的部分不能再保留，其它的词语一律不变)，这个句子就变成了定语从句。然后，再把这个定语从句整个放在被修饰的词后面，最后，如果还有其它句子成分，就把它们放到定语从句的后面，就行了。
　　例如：
　　Have you found the book? You were looking for the book yesterday.
　　在这两个句子中，the book是相同的，定语从句修饰的就是the book。把后面这一句变成定语从句，找个关系词来代替the book;在将要被变成定语从句的名子中，the book是物并作宾语，所以用which或that代替它。
　　然后把which或that放到本句的最前面，其它的词和语序一律不变。这时，就成了"that/which you were looking for yesterday?”，再把这个定语从句整个放在被修饰的词后面，就成了“have you found the book that/which you were looking for yesterday?”定语从句就完成了，主句是问句，所以句末用问号。that/which代替的是原句中的宾语，原句变成了从句，它们仍然作从句的宾语。关系代词在从句中作宾语时可以省略，因此上句又可变成“have you found the book you were looking for yesterday?”.
　　请同学们照上面的例子，把下面变定语从句的步骤说出来(括号里的可以省略):
　　( 1 ) "The dog belongs to the Browns. It ate my fish yesterday."
　　……The dog which/that ate my fish yesterday belongs to the Browns。
　　(2) "The lady has gone to the police station. Her car has been stolen."
　　……The lady whose car has been stolen has gone to the police station.
　　(3) "I' ve seen the film. His girl friend played the leading role In it.''
　　……I' ve seen the film {which / that) his girl friend played the leading role in
　　……I’ve seen the film in which his girl friend played the leading role.
　　……His girl friend played the leading role in the film {which/that) I’ve seen.
　　关系副词与此同理。只是关系副词代替的是原句中的状语。在被代替
　　之前，这个状语中一定要含有一个与另一句相同的成分。