aswhile的用法.doc

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as的用法小结
as可以作连词、介词及关系代词。现将其用法小结如下 ：
一、as作连词的用法：
1. 作”当 的时候",引导时间状语从句。注意与 when、 while的用法区别。
① when作”当……的时候”解,可以指较短的（一点）时间，也可指一段时间。如：
When he was at college, he could speak several foreig n Ian guages.
When the clock struck twelve, all the lights in the street went out.
② while常表示一段较长的时间或一个过程，强调主句谓语动词与从句谓语动词同时 发生。如：
Work while you work. Play while you play.
③ 但属下列情形时，只用as,而不用when或while。
A） 用于表示同一个人的 两种动作交替进行，指"一边 ，一边 "。如：
The girl dan ces as she sings on the stage.
He looked behind from time to time as he went forward.
B） 表示两个同步发展的动作或行为 译为”随着……”。如：
As time went on / by, she became more and more worried.
As children get older, they become more and more interested in the things around them.
C） 表示两个 短促行为或事件 几乎同时发生。如：
I thought of it just as you ope ned your mouth.
Just as the flying worm hit her face, she gave a loud cry.
D） 后接名词表示某一年龄段时，用as。如：
As a young man, he was active in sports.
2. as=since,作"既然"、”由于”解，引导原因状语从句，常用来表示已为 人们所知或显而 易见的原因或理由。如：
As / Since you're not feeling well, you may stay at home.
As he was n't ready in time, we went without him.
3. as=in the way that，作"像"、"按照 的方式”解，引导方式状语从句。如：
He speaks En glish as America ns do.
Remember, you must do everyth ing as I do.
4. 用于as...as..或 not so/ as...as...中，前一个as是副词，后一个as是连词,引导比较状语 从句。女口 :
They helped the o