Descriptive set theory

set that can be constructed from open or closed sets by repeatedly taking countable unions and intersections

topological space that has small inductive dimension zero

in topology, a countable union of nowhere dense subsets

study of well-behaved subsets of Polish spaces

separable, completely metrizable topological space

property of sets in a topological space that differ from open sets by meager sets

the Cartesian product of countably infinitely many copies of the set of natural numbers with the product topology

topological space

countable union of closed sets

countable intersection of open sets

in descriptive set theory, a subset of a Polish space constructible by taking complements and projections of an analytic set

subset of a Polish space that is the continuous image of a Polish space