One of the officials appointed by the pope in the Roman Catholic Church, ranking only below the pope and the patriarchs, constituting the special college which elects the pope. (See Wikipedia article on Catholic cardinals.)
Any of various related passerine birds of the family Cardinalidae (See Wikipedia article on cardinals) and other similar birds that were once considered to be related.
Short for cardinal number, a number indicating quantity, or the size of a set (e.g., zero, one, two, three). (See Wikipedia article on Cardinal number.)