Definition 21.1.2 (Borel Measurable).label Let $(X, \cm)$ be a measurable space, $Y$ be a topological space, and $f: X \to Y$ be a mapping, then $f$ is Borel measurable if $f$ is $(\cm, \cb_{Y})$-measurable.
Definition 21.1.2 (Borel Measurable).label Let $(X, \cm)$ be a measurable space, $Y$ be a topological space, and $f: X \to Y$ be a mapping, then $f$ is Borel measurable if $f$ is $(\cm, \cb_{Y})$-measurable.