What does $p_b \propto ρ^n _b $ mean

Question

$p_b \propto ρ^n _b $, in fluid mechanics, where $p_b$ is the pressure inside a bubble and $\rho$ is the density.

What does that symbol looking like alpha mean?

Answer 1

It means that $p_b$ is directly proportional to $ρ^n _b$.

i.e. $p_b = C\rho_b^n$, for some constant $C$ (to be determined).