1、当as作介词时意思是“作为”，例句为：French is known as the most beautiful language in the world.意思为：法语以世界上最优美的语言著称。

2、当as做关系代词时，引导定语从句，例句为：This is the same game as I played yesterday.意思为：这和我昨天玩的游戏一样。

3、当as作连词时，引导原因状语从句时，所表达的意思为因为，例句为：As rain has fallen the air is cooler.意思为：因为下过雨，所以空气比较凉爽。

4、当as作连词引导让步状语从句时，意思是“尽管，虽然”，例句为：Young as he is， he has been one of the most famous painters in our country.意思是：虽然他还很年轻，但是已经成为我国最有名的画家之一。

5、as做连词固定搭配as…as，例句为：My sister is as tall as me.意思是我姐姐和我一样高。

6、当然是作连词时，引导时间状语从句，例句为：My mom was cooking fish as I arrived home.意思为：当我到家时我的妈妈正在做鱼。