定語從句分為限制性定語和非限制性定語從句，兩者都是英語語法學習中的重點和難點，非限制性定語從句在句中主要起補充說明作用，缺少也不會影響全句的理解，這次小編就為大家來講解一下由which和as引導的非限制性定語從句的區(qū)別，一起學起來吧！

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）當定語從句所修飾的主句內(nèi)容是謂語動詞的對象時，常用as，如：

?? She finally stopped crying, as we had expected．

?

（4）當關系代詞代表主句引起的結果，又做主謂賓補（SVOC）結構中的主語時，多用which：

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

（5）在從句中作介詞賓語時，用which，如：

??? They went into a room, in which the muder happened.

（6）在從句中代表主句中的謂語的整個概念時，常用which，如：

??? She can both sing and dance, which I cannot．

好了以上就是為大家?guī)淼膚hich和as引導的非限制性定語從句的區(qū)別了，希望大家在學習中能夠仔細辨析這些區(qū)別，最終達到能輕松分辨不同句式，對各類句型都應用自如的水平。