定语从句的基本用法：
（一）关系代词引导的定语从句
1．who 指人,在定语从句中作主语,有时也作宾语.
2.whose 通常指人,也可指物,在定语从句中做定语.
3．whom 指人,在定语从句中做宾语,常可省略.
指物时,常用下列结构来代替：
The classroom whose door is broken will soon be repaired.
＝The classroom the door of which is broken will soon be repaired.
Do you like the book whose cover is yellow?
＝Do you like the book the cover of which is yellow?
4．which 指物,在定语从句中做主语或宾语,做宾语时常可省略.
5．that 引导定语从句时,既可以指人,也可以指物.指人时,相当于who 或whom；指物时,相当于which..在定语从句中作主语或宾语,作宾语时常可省略.
定语从句考查重点：
（一）定语从句在下列情况下只能用that,而不能用which指物.（指人时可以用who/whom）
1.当先行词被形容词最高级或者序数词修饰时.
2.当先行词是不定代词everything,anything,nothing ,something,all,none,few,little,some,much等代词时,或当先行词受every,any,all,some,no,little,few,much等代词修饰时
3.当先行词被the very,the only,the same,the last修饰时
4.当先行词是who,或which引导的主句时
5.当先行词为人与动物或人与物时