考研英语中，as是一个重要的介词，查字典公务员考研建议17年考生在复习考研英语语法的时候，把单词as的用法研究透彻，这样不论是出现在什么题型里面，大家都能正确辨识它的含义。
一、As用作副词
在asas结构中，第一个as是副词，其后常接形容词或另外的副词，第二个as则是连词。
99翻译中一句经典的话：While there are almost as many definitions of history as there are historians, modern practice most closely conforms to one that sees history as the attempt to recreate and explain the significant events of the past.
在这里中就包含一个asas结构，第一个as即为副词，修饰形容词many,而第二个句中是就是比较状语从句的连词。
二、as用做介词，与一些动词搭配
As常用再一些固定搭配中，比如defineas，viewas, seeas, useas, regardas, envisionas.., think ofas, refer toas, classifyas
例如06年翻译中讨论的一句话：
I shall define him as an individual who has elected as his primary duty and pleasure in life the activity of thinking in Socratic way about moral problems.
在这里存在了两个as，也同时也存在两种结构defineas和elected as. 第一个很好判断，是典型的as作为介词，翻译成作为，而后者乍看上去并不太好理解，因为结构发生了一定调整，elect该词后真正的宾语是the activity of thinking in Socratic way about moral problems,因头重脚轻，发生了位置的移动。
第二，as有时单独作用，译为作为，例如常用的as a student，as a leader of the department等。
三、As用作连词
As用作连词，绝大多数情况是引导一系列的状语从句。
1、引导时间状语从句
As the sun rises from the foothill of Mountain Song, thousands of marital artists are kicking, punching and spinning their swords and spears in union at the open parade ground.
当太阳从嵩山脚下升起的时候，成千上万的武术家在开放的练兵场中拳打脚踢，整齐划一地挥舞着矛与剑。
2、引导原因状语从句
04年翻译We are obliged to them because some of these languages have since vanished, as the peoples who spoke them died out or became assimilated and lost their native language.
在该句中存在两个原因状语从句，一个是由because引导，另一个则是as引导，解释some of these languages have since vanished的原因。
3、引导方式状语从句
I hope all the precautions against air pollution, as suggested by the local government, will be seriously considered there.
方式状语从句中，as 后省略了主谓结构it is, as 的含义则为正如，正像。
4、引导让步状语从句
作文模板中的经典模板句Simple as it is, what the picture conveys to us is thought-provoking. 谨记as只有在引导状语从句中要倒装，意义和though类似。
当然还有在定语从句中也会出现，这里在定语从句的文章中有明确说过，这里就不再详述了
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