a classificatory division in any field of knowledge, as a phylum or any of its subdivisions in biology.
(in Aristotelian philosophy) any of the fundamental modes of existence, such as substance, quality, and quantity, as determined by analysis of the different possible kinds of predication.
(in Kantian philosophy) any of the fundamental principles of the understanding, as the principle of causation.
any classification of terms that is ultimate and not susceptible to further analysis.
Also called a game in which a key word and a list of categories, as dogs, automobiles, or rivers, are selected, and in which each player writes down a word in each category that begins with each of the letters of the key word, the player writing down the most words within a time limit being declared the winner.
a type of mathematical object, as a set, group, or metric space, together with a set of mappings from such an object to other objects of the same type.