Number of open sets for a topology with a countable basis

2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/152860Let T be the family of open subsets of a topological space (not necessarily Hausdorff or even T_0). We prove that if T has a countable base and is not countable, then T has cardinality at least continuum.LogicGeneral TopologyNumber of open sets for a topology with a countable basistext