EntityQ1656686· pop 8· linked from 127 articlesidealSign in to savein order theory, a nonempty, upward‐directed, downward‐closed subset of a preordered setConnectionspartially ordered setEntityidealEntitylatticeEntityinfimum and supremumEntityordered fieldEntitywell-founded relationEntityordered groupEntitycomplete partial orderEntityweak orderingEntityordered vector spaceEntitymathematicsEntityInternational Standard Book NumberEntitytopologyEntitydigital object identifierEntityabstract algebraEntityempty setEntityQ180686EntitybibcodeEntityisomorphismEntityQ118398EntityCategoriesIdeals (ring theory)Order theory