先行词是限制性定语从句不可缺少的部分，去掉它主句意思往往不明确。以下是高考英语一轮复习必考知识点，精品学习网希望对考生复习有帮助。

在as引导的非限制性定语从句中，连接代词as在句子中可以作主语、宾语或表语等，可以指人或物。其在定语从句中的位置比较灵活，即可以在句子 前面，在句子中间或句子末尾。常用的结构有：as we all know; as is well known to…; as is often the case; as is said/mentioned above; as has been said before; as I told you before; as is evident; as often happens; as can be seen; as is/was expected; as we expect; as I can remember等。

[注意1]as通常只指整个句子的内容，不表示部分内容。

[注意2]as引导的非限制性定语从句通常指"事先可以预料到的""料想到的"，表达"好"的方面。

[注意3]as引导限制性定语从句时，常构成the same…as…; such…as…; so/as …as…等结构。在从句中既可以指人、物，也可以指整个句子。

[例句]

This is also part of your work, as I told you before. 我曾告诉过你，这也是你工作的一部分。

The man was a teacher, as was evident from his way of speaking. 从那人说话的样子可明显看出，他是个老师。

Such ideas as he hits on are worthless. 像他那样偶然想起的主意是无用的。

It's the same story as I heard from her yesterday. 这故事跟我从她那儿听到的相同。

He will marry as pretty a girl as he can find. 他要尽可能找漂亮的女孩结婚。

Such people as have made great contributions to the world should be greatly respected.

那些对世界做出巨大贡献的人们应该受到极大的尊重。

高考英语一轮复习必考知识点：as引导的非限制性定语从句的内容就是这些，精品学习网预祝考生可以获得满意的成绩。

相关链接

2017高考英语语法复习重要知识点：介词前置 

高考英语一轮复习语法讲解：定语从句中的主谓一致