I am not aware of any special meaning in math. In physics, it is short for pascal, a unit of pressure.
PA Stand For Pennsylvania
It doesn't stand for bananas.
3000
metre
elementary maths
It doesn't "stand for" anything. And wrong category.
maths economics comers
An unknown number.
LCM stand for Least Common Multiple
Public Address
Base times Height
pa = Per Annum / Per Year