Definition:Sigma-Discrete Set of Subsets
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Definition
Let $T = \struct {S, \tau}$ be a topological space.
A $\sigma$-discrete set of subsets is a set of subsets of $S$ which is the countable union of discrete set of subsets.
Sources
- 1955: John L. Kelley: General Topology: Chapter $4$: Embedding and Metrization
- 1970: Stephen Willard: General Topology: Chapter $6$: Compactness: $\S20$: Paracompactness: Definition $22.2$