🌐EnglishEnglishDeutschEspañolFrançaisItalianoNederlandsPolskiPortuguêsTiếng ViệtTürkçeРусскийالعربيةفارسی한국어中文日本語EntityQ175116· pop 21· linked from 293 articlesdiscrete spacetopological space whose every subset is both open and closedAvailable in 21 languagesEspañolFrançaisDeutsch中文日本語РусскийPortuguêsItalianoالعربيةEsperantoFinnishConnectionsmetric spaceEntitycountable setEntityCategoriesGeneral topologyMetric spacesTopological spaces