as 的用法：as 作介，用法和一，其含“作”。

但是as 作性，其用法和功能多，可以引各从句，as 引原因状从句、状
从句、方式状从句、步状从句和定从句。

as 的用法
1、 as 做介，意思是“作”
例句：
French is known as the most beautiful language in the world.
法以世界上最美的言著称。

2、 as 做，引状从句，意思是“当⋯⋯的候”
例句：
My mother was cooking fish as I arrived home.
当我到家的候，我正在做。

3、 as 做，引原因状从句，意思是“因”
例句：
As rain has fallen, the air is cooler.
因下雨，所以空气比凉爽。

4、 as 做，引步状从句，意思是“ 然”
例句：
Young as he is, he has been one of the most famous painters in our country.
然他很年，但已成我国家最有名的画家之一。

5、 as 做，引方式状从句，意思是“以⋯⋯方式”
例句：
Do as the Romans do when in Rome.
入乡随俗
6、 as 做关系代词，引导定语从句
例句：
This is the same game as I played yesterday. 这和我昨天玩的游戏一样。