1、as作副词使用时是同样地、一样地、例如的意思，看例句，It's not as good as it used to be. 这个不如以前好了。She'll soon be as tall as her mother. 她很快就会和她母亲一样高了。
2、as也可以作为介词，是以…的身份；作为的意思，举个例子，She works as a waitress. 她是名服务员。
3、而当as作为连词时是因为，有由于或是随着的意思，例如，As it was getting late, I decided to book into a hotel. 因为天色已晚，我决定找家旅馆投宿。I saw him as I was coming into the building. 我进楼时看到了他。
