(mathematical analysis) A collection of subsets of a given set, such that the empty set is part of this collection, the collection is closed under complements (with respect to the given set) and the collection is closed under countable unions.

(mathematical analysis, of a set in a topological space) That is expressible as a countable union of compact sets.

(mathematical analysis) countable additivity

plural of σ-algebra

(mathematical analysis) The smallest σ-algebra which contains the topology of a given topological space.

(mathematical analysis) A set, in a measurable space, that is expressible as a countable union of sets of finite measure.

plural of Borel σ-algebra

plural of σ-finite measure