CONTRARIES
n.[See Contrary. ] In logic, propositions which destroy each other, but of which the falsehood of one does not establish the truth of the other. If two universals differ in quality, they are contraries; as, every vine is a tree; no vine is a tree. These can never be both true together; but they may be both false.
Con "tra *ries ( or, n. pl. Etym: [Pl. of Contrary, n.] (Logic )