Sagacity: acuteness of mental discernment and soundness of judgment.

1548, from M.Fr. sagacité, from L. sagacitatem (nom. sagacitas) "quality of being acute," from sagax (gen. sagacis) "of quick perception," related to sagus "prophetic," sagire "perceive keenly," from PIE base *sag- "to track down, trace, seek" (cf. O.E. secan "to seek;" see seek). Also used 17c.-18c. of animals, meaning "acute sense of smell."

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