as非限定性定語從句
導(dǎo)語：定語從句又分為限制性與非限制性定語從句，下面小編講解as非限定性定語從句，歡迎參考。
關(guān)系代詞 as 用于引導(dǎo)非限制性定語從句時(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)的非限制性定語從句可以放在句子的最前面，而which引導(dǎo)的定語從句不能放在句首。
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)的非限制性定語從句可以放在句子的中間，which引導(dǎo)的定語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。
Taiwan is, as you know, an inseparable part to China.
眾所周知，臺灣是中國不可分割的一部分。
拓展
（一）非限定性定語從句as引導(dǎo)
as引出非限定性定語從句時(shí)，代替整個(gè)主句，對其進(jìn)行說明但通常用于像as we all know, as it is known, as is known to all, as it is, as is said above, as always mentioned above, as is usual, as is often the case, as is reported in the newspaper等句式中。as在非限定性定語從句中作主語、表語或賓語，且引出的從句位置比較靈活，可位于句首或句末，也可置于主句中間。通常均由逗號將其與主句隔開。as有“正如……， 就像……”之意。
如：As is known to the United States, Mark Twain is a great American writer.
美國人都知道，馬克·吐溫是一位偉大的美國作家。（as在從句中作主語）
He forgot to bring his pen with him, as was often the case.
他忘了帶筆，這是常事。（as在從句中作主語）
He is absorbed in work, as he often was.
他正在全神貫注地工作，他過去經(jīng)常這樣。（as在從句中作表語）
As we all know, the earth is round.
眾所周知，地球是圓的。（as在從句中作賓語）
The two brothers were satisfied with this decision，as was agreed beforehand.
兩兄弟對此決定都滿意，這項(xiàng)決定在事前都已得到他們的同意。(as在從句中作主語)
Taiwan is，as you know，an inseparable part of China.
你知道，臺灣是中國不可分割的一部分。(as在從句中作賓語)
“介詞+關(guān)系代詞”引導(dǎo)非限制性定語從句：在介詞后引導(dǎo)非限制性定語從句。
難：句意相同
as it is known to all (that...) (as 做狀語從句連詞，是狀語從句, 可以加that)
與 as is known to all (as做主語，是定語從句)
與 it is known to all that... (主語從句，it是形式主語)
即：As is widely known, the moon is closer to the us than the sun.(定從)
= That the moon is closer to the us than the sun is widely known.(主從)
= It is widely known that the moon is closer to the us than the sun.(主從)
As it is known to everyone, I thought you knew about it too.(狀從)[1]
關(guān)系代詞which有時(shí)并不代表主句中某一確定的詞，而是概括整個(gè)主句的意思。介詞的`選擇取決于它與先行詞的搭配或與從句中謂語動(dòng)詞的搭配。
They were short of sticks to make frames for the climbing vines，without which the yield would be halved.
他們?nèi)贝钇咸鸭艿臈U兒，沒有它們產(chǎn)量會減少一半。
They thanked Tom，without whose support they would not have succeeded.
他們很感激Tom，沒有他的支持他們是不會成功的。
（二）as, which 非限定性定語從句
由as, which 引導(dǎo)的非限定性定語從句，as和which可代整個(gè)主句，相當(dāng)于and this或and that，as, which 非限定性定語從句。As一般放在句首，which在句中。
As we know, smoking is harmful to one's health.
The sun heats the earth, which is very important to us.
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