Definition:Sigma-Discrete Basis
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Definition
Let $T = \struct {S, \tau}$ be a topological space.
A $\sigma$-discrete basis for $T$ is a basis which is the countable union of discrete sets of open sets.
Sources
- 1955: John L. Kelley: General Topology: Chapter $4$: Embedding and Metrization
- 1970: Stephen Willard: General Topology: Chapter $6$: Compactness: $\S20$: Paracompactness: Definition $22.2$
- 1978: Lynn Arthur Steen and J. Arthur Seebach, Jr.: Counterexamples in Topology (2nd ed.): Part $\text {III}$: Metrization Theory: Conjectures and Counterexamples: Screenabble Spaces