1.由关系代词 who， whom ， whose， that ， which；关系副词 when ，
where ， why引导。

    （下面十个句子请读5 遍并脱口译出！）

    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.

    2.只能用that和who 引导的定语从句

    A.all ， nothing， anything ， a few， one做先行词指物时B.先行词前
有形容词最高级修饰时，后面常跟that而不是which 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。

    3.as引导定语从句

    A.引导限制性语从句。

    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。

    B.as引导非限制性定语从句时，作用与which 相同，as作为关系代词代替整
个主句。

    （这是语法考试的一个考点。）

    注意区别：as引导的从句用于句首、句中或句后，而which 引导的定语从句
不能放在句首。

    e.g. As is reported ， a foreign delegation will visit the city.据
报道，一个外国代表团将访问这个城市。