關(guān)系代詞 as 用于引導(dǎo)非限制性定語(yǔ)從句時(shí)，應(yīng)注意以下三點(diǎn)：

一. as引導(dǎo)的非限制性定語(yǔ)從句位于句末時(shí)，一般可以和which互換。

the author was brought up in a small village, as (which) is recounted in some of his stories.
作者是在一個(gè)小村莊里長(zhǎng)大的，這個(gè)問題在他的一些小說了就被提到過。

she is extremely popular among the students, as (which) is common knowledge.
她在學(xué)生中間很受歡迎，這是普遍知道的。
 
但是，當(dāng)主句是否定句時(shí)，as和which就不能互換，因?yàn)閍s引導(dǎo)的非限制性定語(yǔ)從句不包含否定意義。

spiders are not insects, as many people think.
蜘蛛不是昆蟲，而許多人卻認(rèn)為蜘蛛是昆蟲。
 
二. as引導(dǎo)的非限制性定語(yǔ)從句可以放在句子的最前面，而which引導(dǎo)的定語(yǔ)從句不能放在句首。

as is often the case, the girl forgot to her dictionary.（不能用which）
經(jīng)常是這樣子的，那個(gè)女孩忘了帶字典。

as you will find out, all is now settled.
你將會(huì)看到這樣的情況，一切都已搞定了。
 
三. as引導(dǎo)的非限制性定語(yǔ)從句可以放在句子的中間，which引導(dǎo)的定語(yǔ)從句也可以放在句子的中間。

water, which is a clear liquid, has many uses.
水是一種透明的液體，有許多用途。

Chinese Taiwan is, as you know, an inseparable part to china.
眾所周知，中國(guó)臺(tái)灣是中國(guó)不可分割的一部分。