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我們都知道，which和as都可以引導(dǎo)非限制性定語從句，有時(shí)可以互換使用。但兩者的用法又有所不同。何時(shí)用which，何時(shí)又必須用as？是不是有些傻傻分不清？！來來來，今天就把這個問題一次拎清~~~

（1）位置上，as可放在句首、句末，也可插入主句中；which一般放在主句之后（有時(shí)也可用as）：

??? As we all know, reading is very important.

??? Reading is very important, which we have already known when we were very young.

（2）意義上，as有正如、按照、正像之意，一般用在肯定句中；which可用于含肯、否定意義的句子中：

??? He failed in the exam again, as was expected．

??? He failed in the exam again, which was unexpected．

?（3）當(dāng)定語從句所修飾的主句內(nèi)容是謂語動詞的對象時(shí)，常用as，如：

??? Jack was admitted into the university, as we had expected．

?（4）固定結(jié)構(gòu)，用as：

??? as has been said before ?????????as often happens

??? as is well known ?????????? ???????? as we all can see

??? the same...as???????????????????????? such...as

（5）當(dāng)關(guān)系代詞代表主句引起的結(jié)果，又做主謂賓補(bǔ)（SVOC）結(jié)構(gòu)中的主語時(shí)，多用which：

??? He passed the exam, which made him delighted．

（6）在從句中作介詞賓語時(shí)，用which，如：

??? They went to the zoo, after which they saw a film.

（7）在從句中代表主句中的謂語的整個概念時(shí)，常用which，如：

??? He can write a letter in English, which I cannot．

（8）指代主句中某一名詞時(shí)，多用which，如：

??? Beijing, which he was born, is our capital.

（9）代替主句中的形容詞時(shí), 常用which，如：

??? Lily thought me clever, which she herself was.

在定語從句中，相比于which VS that，who VS that，我們對which與as兩者區(qū)別的關(guān)注度要少很多，在遣詞造句或是口語表達(dá)中，也常常是“跟著感覺走”。希望本篇能幫助大家減少關(guān)系代詞的錯用，從而準(zhǔn)確清晰地掌握關(guān)系代詞這一語法點(diǎn)~~~