EntityQ320369· pop 19· linked from 69 articlesclopen setSign in to savesubset that is both open and closedConnectionsintervalEntityconnected spaceEntitydiscrete spaceEntityInternational Standard Book NumberEntitydoorEntitytopologyEntityrational numberEntityempty setEntityOCLC, Inc.Entitymetric spaceEntityunionEntitysquareEntityintersectionEntitytopological spaceEntitynumber lineEntityblend wordEntitycomplementEntityopen setEntitydisjoint setsEntityinfinite setEntityCategoriesGeneral topology