在as引導的非限制性定語從句中，連線代詞as在句子中可以作主語、賓語或表語等，可以指人或物。其在定語從句中的位置比較靈活，即可以在句子前面，在句子中間或句子末尾。常用的結構有：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通常只指整個句子的內容，不表示部分內容。
[注意2]as引導的非限制性定語從句通常指“事先可以預料到的”“料想到的”，表達“好”的方面。
[注意3]as引導限制性定語從句時，常構成the same…as…; such…as…; so/as …as…等結構。在從句中既可以指人、物，也可以指整個句子。
[例句]
This is also part of your work, as I told you before. 我曾告訴過你，這也是你工作的一部分。
The man was a teacher, as was evident from his way of speaking. 從那人說話的.樣子可明顯看出，他是個老師。
Such ideas as he hits on are worthless. 像他那樣偶然想起的主意是無用的。
It’s the same story as I heard from her yesterday. 這故事跟我從她那兒聽到的相同。
He will marry as pretty a girl as he can find. 他要儘可能找漂亮的女孩結婚。
Such people as have made great contributions to the world should be greatly respected.
那些對世界做出巨大貢獻的人們應該受到極大的尊重。
