关系代词：that, which, who, whom, whose代指先行词。
关系副词：when, where, why作时间状语。
1. that 和which
His father works in a factory that/which makes TV sets.
Who was hurt in the accident that/which happened yesterday?
The coat (which/that) I put on the desk is black.
注意：The room in which I live is very big. (在介词后面不能用that)
This is the most interesting story (that) I have ever heard.
The children like the second lesson that is about “The Football Match”.
3)先行词被the only，the very 或the same等修饰，定语从句只能用that引导。
It is the only word (that) I know in the passage.
Where is the very book (that) I bought just now?
This is the (same) bicycle (that) I lost.
I want everything (that) I want.
I am writing to tell you about something very strange that happened to me last week.
5)先行词被不定代词all, any, no, every, little, much, many修饰时，只能用that
Here is all the money (that) I have.
I can remember well the persons and some pictures (that) I see in the room.
7)定语从句所修饰的词为the one 时，定语从句用that引导
Is it the one(that)you want?
Who is the girl that won the first place?
Who is the teacher that Xiao Li is talking to?
The doctor with whom she went to the United States last month is very famous.
=The doctor who/whom/that she went to the United States with last month is very famous.
I still remember the day when I first came to Beijing. when=on which
This is the house where I lived two years ago.
We don’t know the reason why he was late for school.