°A group, often named or numbered, to which items are assigned based on similarity or defined criteria.
"This steep and dangerous climb belongs to the most difficult category."
°A collection of objects, together with a transitively closed collection of composable arrows between them, such that every object has an identity arrow.
"One well-known category has sets as objects and functions as arrows."
synonyms: class, family, genus, group more» , kingdom, order, phylum, race, tribe, type