Definition 5.11.1 (Saturated).label Let $X, Y$ be sets, $f: X \to Y$ be surjective, and $E \subset X$, then $E$ is saturated with respect to $f$ if $E = f^{-1}(f(E))$.
Definition 5.11.1 (Saturated).label Let $X, Y$ be sets, $f: X \to Y$ be surjective, and $E \subset X$, then $E$ is saturated with respect to $f$ if $E = f^{-1}(f(E))$.