Categories are either classes under which all our Notions of things may be grouped, or classes under which all our Thoughts of things may be grouped; the former called Logical, we owe to Aristotle, and the latter called Metaphysical, we owe to Kant. The Logical, so derived, that group our notions, are ten in number: Substance or Being, Quantity, Quality, Relation, Place, Time, Position, Possession, Action, Passion. The Metaphysical, so derived, that group our thoughts, are twelve in number: (1) as regards quantity, Totality, Plurality, Unity; (2) as regards quality, Reality, Negation, Limitation; (3) as regards relation, Substance, Accident, Cause and Effect, Action and Reaction; (4) as regards modality, Possibility and Impossibility, Existence and Nonexistence, Necessity and Contingency. John Stuart Mill resolves the categories into five, Existence, Co-existence, Succession, Causation, and Resemblance.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Categorical imperative * Catesby, Mark