as在定语从句中是什么意思？怎么用？as定语从句例句有哪些呢？
定语从句as造句的句子
(1) As is known to all, China is a developing country.
(2) He is from the south, as we can see from his accent.
(3) John, as you know, is a famous writer.
(4) As a student，I am supposed to work hard.
定语从句中as的用法
引导状语从句的连词as可以用作关系代词，引导定语从句，因而被称作准关系代词。
1.准关系代词as引导限制定语从句，用于以下3个结构中，as在从句中作主语、宾语或表语：
a.so / such…as
Such people as were mentioned by him were honest. (as作主语)
I’ve never seen such a clever man as he is. (as作表语)
Last term our maths teacher set so difficult an (= such a difficult) examination problem as none of us worked out.
b.the same…as
Modern statemen are often faced with the same problem as defeated the ancient Romans. (as 作宾语)
I like the same book as you do. (as 作宾语)
c.as…as
As many children as came were given some cakes. (as 作主语)
He is as diligent a man as ever lived. (as 作主语)
补充：
a.such…as 与 such…that的区别
such…as 引导定语从句；such…that引导结果状语从句。
They talked in such simple English as children could understand.
他们用孩子们能听懂的简单的英语交谈。
They talked in such simple English that children could understand it.
他们用十分简单的英语交谈，连孩子们都能听懂。
I will provide you with such things as you may need.
我要供给你一些你可以用得着的东西。
He shut the window with such a force that the glass broke.
他如此用力地关门，结果玻璃碎了。
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