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c.1300, from Old French levier (Modern French leveur) "a lifter, a lever," agent noun from lever "to raise," from Latin levare "to raise," from levis "light" in weight, from PIE root *legwh- "light, having little weight; easy, agile, nimble" (cf. Sanskrit laghuh "quick, small;" Greek elakhys "small," elaphros "light;" Old Church Slavonic liguku, Lithuanian lengvas "light;" Old Irish laigiu "smaller, worse;" Gothic leihts, Old English leoht "light" (adj.)). As a verb, 1856, from the noun.
A simple machine consisting of a bar that pivots on a fixed support, or fulcrum, and is used to transmit torque. A force applied by pushing down on one end of the lever results in a force pushing up at the other end. If the fulcrum is not positioned in the middle of the lever, then the force applied to one end will not yield the same force on the other, since the torque must be the same on either side of the fulcrum. Levers, like gears, can thus be used to increase the force available from a mechanical power source. See more at fulcrum, See also mechanical advantage.