as的几种用法：1.做连词，固定搭配as……as，意思是“和……一样”；2.做连词，表示“当……的时候”；3.做连词，表示“因为”4.做连词，表示“尽管”等。
1.as做连词，固定搭配as……as，意思是“和……一样”
例句：
My sister is as tall as me.
我姐姐和我一样高。
He runs as fast as me/I.
他和我跑得一样快。
She is as beautiful as me/I.
她和我一样漂亮。
Being a mother isn't as bad as I thought at first!
做一位母亲并不像我当初想的那样糟！
2.as做连词，引导时间状语从句，意思是“当……的时候”
My mother was cooking fish as I arrived home.
当我到家的时候，我妈妈正在做鱼。
I was always hard up as a student.
我当学生时总是很拮据。
The crowd cheered as she went up the steps to the bandstand.