EntityQ219448· pop 5· linked from 32 articlesprojective setSign in to savein descriptive set theory, a subset of a Polish space constructible by taking complements and projections of an analytic setConnectionsInternational Standard Book NumberEntitynatural numberEntitynumber lineEntitycomplementEntityordinal numberEntityopen setEntitySpringer Science+Business MediaEntityuncountable setEntityclosed setEntityrecursive setEntityBorel setEntityprojectionEntityclopen setEntityPolish spaceEntitydescriptive set theoryEntityrecursively enumerable setEntityfirst uncountable ordinalEntityBaire spaceEntityFσ setEntityCantor spaceEntityCategoriesDescriptive set theoryMathematical logic hierarchies