DECADE

noun Etymology: Middle English, from Middle French décade, from Late Latin decad-, decas, from Greek dekad-, dekas, from deka Date: 15th century a group or set of 10: as, a period of 10 years, a division of the rosary that consists primarily of 10 Hail Marys, a ratio of 10 to 1 ; order of magnitude , decadal adjective