coefficient (n.)

also co-efficient, c. 1600, "that which unites in action with something else to produce a given effect," from co- + efficient. Probably influenced by Modern Latin coefficiens, which was used in mathematics in 16c., introduced by French mathematician François Viète (1540-1603). As an adjective, "acting in union to the same end," from 1660s. Related: Coefficiency.