A1 used to describe something’s purpose or someone’s job: She works as a waitress. They use their spare bedroom as an office.
as… as A2 used to compare two things, people, amounts, etc.: He’s not as tall as his brother. She earns three times as much as I do.
A2 because: You can go first as you’re the oldest.
B1 while: I saw James as I was leaving.
B1 in the same way: This year, as in previous years, tickets sold very quickly.
as if/as though › used to describe how a situation seems to be: It looks as if it might rain.
as for › used to talk about how another person or thing is affected by something: I’m pleased. As for Kyle, I don’t care what he thinks.