1. 定语从句的定义：

　　2. 定语从句的关系词：

　　3. 由“介词+关系代词”作介词宾语引导的定语从句：

　　注意点：

　　1)介词后面的关系词不能省略。

　　2)that前不能有介词。

　　3)某些在从句中充当时间，地点或原因状语的“介词+关系词”结构可以同关系副词when, where和why互换。

　　This is the house in which I lived two years ago.

　　4)固定搭配的词组，不能把介词提到关系代词前。

　　(正)He has a little son (whom/that) he has to look after.

　　(误)He has a little son after whom he has to look.

　　4. 只用关系代词that的情况：补充

　　1)当先行词是all，everything，nothing，something，anything，little，much等不定代词时

　　Is there anything (that) you don't understand?

　　2)先行词被all，every，no，some，any，little，much等修饰时。

　　You can take any seat that is free.

　　3)当先行词前面有the only，the very，the last等修饰时。

　　He is the only person that can help you out.

　　4)当序数词或形容词最高级修饰先行词时。

　　This is the second time that you told us the story.

　　This is the best book that I have ever read.

　　5)先行词同时含有人和物时。

　　We talked about the things and people that we were interested in.

　　6)当主句是以疑问词who或which开头的特殊疑问句时。

　　Who is the boy that is playing football?