1.由关系代词 who, whom, whose, that, which; 关系副词 when, where, why 引导。
e.g.1. The death notices tell us about people who have died during the week.
2. The man (whom) you spoke to just now is my friend.
3. The building whose lights are on is beautiful.
4. Please find a place which we can have a private talk in.
5. The knee is the joint where the thighbone meets the large bone of the lower leg.
6. He still remembers the day when he went to school.
7. It is no need telling us the reason why you didn't finish it in time.
8. He has three sons, two of whom died in the war.
9. Mr. Smith, whose wife is a clerk, teaches us English.
10. In the Sunday paper there are comics, which children enjoy.
A.all, nothing, anything, a few, one做先行词指物时
C.先行词前有 the only, the first, the last, the next, the very等词修饰时，引导词只能用that
D.当先行词是 anyone, anybody, everyone, everybody, someone, somebody时，后面要用who或whom
e.g. All that glitters is not gold. 闪光的并非都是金子。
在此类定语从句中，as常与主语中作为其先行词的such, the same或as联用构成，"such... as"，"the same... as"和"as ...as"句型，可代替先行词。
e.g. We hope to get such a tool as he is using. 我们希望得到他正在用的那种工具。
e.g. As is reported, a foreign delegation will visit the city.