众所周知,which与as都可以引导定语从句,但它们有许多用法上的区别,现就此简要分析如下:
一、which与as引导非限制性定语从句的区别:
1.Which只能放在主句后面,而as引导的从句位置相对较灵活,可在前,可在中,也可在后。例如:
A) As he realized, I was very useful to him.(在前)
B) Air, as we know, is a gas.(在中)
C) He was a foreigner,as I know from his accent.(在后)
2.在which引导的定语从句中,谓语动词若是am, is, are则这些系动词不能省略;而as后面若是这种情况,则可以省略。例如:
A) He is a teacher, as (is) clear from his manner.(is可以省略)
B) He said he had never seen her before, which was not true.(was不可省略)
3.当which引导的从句在意义上近乎并列关系时,可以用and this,and that代替,意思是“这件事”例如:
A) He changed his mind, which(and this, and that)made me very angry.他改变了主意,这使我很生气。
B) She has married again, which(=and this, and that)was unexpected.出乎意料的是,她又结婚了。
而as主要起与上下文连接的作用,表达说话人的看法、观点,并指出主句内容的出处或根据等,例如:
C)Einstein, as we know, is a famous scientist.爱因斯坦,众所周知,是位伟大的科学家。
D)As is announced in today's newspaper, we must improve our style of work.今天的报纸上说,我们必须改进工作作风。