Definition 18.2.1 (Borel $\sigma$-Algebra).label Let $(X, \topo)$ be a topological space, then the Borel $\sigma$-algebra $\cb_{X}$ on $X$ is the $\sigma$-algebra generated by $\topo$.
Definition 18.2.1 (Borel $\sigma$-Algebra).label Let $(X, \topo)$ be a topological space, then the Borel $\sigma$-algebra $\cb_{X}$ on $X$ is the $\sigma$-algebra generated by $\topo$.