1、as做介词，意思是作为。2、as做连词，引导时间状语从句，意思是当……的时候。3、as做连词，引导原因状语从句，意思是因为。4、as做连词，引导让步状语从句，意思是虽然。5、as做连词，引导方式状语从句，意思是以……方式。6、as做关系代词，引导定语从句。

例句：French is known as the most beautiful language in the world.法语以世界上最美丽的语言著称。My mother was cooking fish as I arrived home.当我到家的时候，我妈妈正在做鱼。Young 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。