定语从句是英语中一个非常重要的句式，同学们应该认真学习，同时在使用过程中也有一些需要注意的问题，小编总结了主要有以下几点：
1、关系代词在句中中作主语时，从句的谓语动词用单数还是复数应由先行词决定
The man who lives downstairs speaks English fluently.
住在楼下的那个人英语说得很流利
The students who are in Grade Three are going to climb the hill tomorrow.
3年纪的学生明天去爬山
2、定语从句有时不直接紧靠着先行词，中间由一个定语、状语或谓语隔开
There is an expression in his eyes that I can't understand.
在他的眼睛里有一种我不明白的神情
This is the room in which （=where） Lu Xun once lived.
这是鲁迅曾经过的房间
4、当定语从句中谓语动词是带介词或副词的短语动词时，短语动词的各个固定的部分不要拆开
The dictionary which you are looking for is on the desk.
你去寻找的那本词典在桌子上
5、注意介词与关系代词的位置：介词在关系代词前，只能用which和whom，且不能省略；介词在词尾，关系代词可用which，that，whom，口语中也可用who，且可省略
The man （whom/who/that） you were talking about has come to school.
你们刚才在谈论的那个人已经来到我们学校
Who‘s the comrade whom you just shook hands with？（或：Who is the comrade with whom you just shook hands？）
刚才与你握手的那个人是谁？
6、关系代词和关系副词在从句中充当一个成分，因此，使用时要注意在从句中避免句子成分的重复出现，试比较：
Let me have a look at the dictionary that you bought it yesterday （误）
Let me have a look at the dictionary that you bought yesterday （正）
请给我看一看你昨天买的那本词典
This is the house where I lived in two years ago. （误）
This is the house where I lived two years ago （正）
这是我两年前住过的房子
