<philosophy of science, logic> a pair of categorical propositions, each of which is true if and only if the other is false. In the traditional square of opposition, an A proposition and its corresponding O proposition are contradictories, as are an E proposition and its corresponding I proposition. Thus, for example: "All dogs are mammals and Some dogs are not mammals" are contradictories, as are "No fish are tuna and Some fish are tuna."
[A Dictionary of Philosophical Terms and Names]
Try this search on OneLook / Google