Definition:Basis (Topology)/Analytic Basis/Definition 2

Definition
Let $\struct {S, \tau}$ be a topological space.

Let $\BB \subseteq \tau$.

Then $\BB$ is an analytic basis for $\tau$ :
 * $\forall U \in \tau: \forall x \in U: \exists V \in \BB: x \in V \subseteq U$

Also see

 * Equivalence of Definitions of Analytic Basis