LEV'ER, noun [Latin levo, to raise.]
In mechanics, a bar of metal, wood, or other substance, turning on a support called the fulcrum or prop. Its arms are equal, as in the balance; or unequal, as in steelyards. It is one of the mechanical powers, and is of three kinds, viz. 1. When the fulcrum is between the weight and the power, as in the handspike, crowbar, etc. 2. When the weight is between the power and fulcrum, as in rowing a boat. 3. When the power is between the weight and the fulcrum, as in raising a ladder from the ground, by applying the hands to one of the lower rounds. The bones of animals are levers of the third kind.