1、as做介词，意思是“作为”
ch is known as the most beautiful language in the world.法语以世界上最美丽的语言著称。
mother was cooking fish as I arrived home.当我到家的时候，我妈妈正在做鱼。
3、as做连词，引导原因状语从句，意思是“因为”
rain has fallen, the air is cooler. 因为下过雨，所以空气比较凉爽。
4、as做连词，引导让步状语从句，意思是“虽然”
g as he is, he has been one of the most famous painters in our country. 虽然他还很年轻，但已经成为我们国家最有名的画家之一。
5、as做连词，引导方式状语从句，意思是“以……方式”
as the Romans do when in Rome. 入乡随俗
6、as做关系代词，引导定语从句
is the same game as I played yesterday.这和我昨天玩的游戏一样。