The simple machine consisting of a rigid bar pivoted at a fixed point is a lever.
The fixed pivot is called the fulcrum. When effort is applied to one part of the bar, the lever transfers that force to a load at another point. A longer distance from the fulcrum can provide greater mechanical advantage, allowing a relatively small effort to move a heavier load—though usually over a smaller distance.
Levers are traditionally divided into three classes according to the positions of the fulcrum, effort, and load. A seesaw is a first-class lever, a wheelbarrow is a second-class lever, and tweezers are a third-class lever. The human arm and the tiny bones of the middle ear also operate as lever systems.
The lever is one of the six classical simple machines identified by Renaissance-era scholars. It does not create energy: an ideal lever trades force for distance, conserving work. Real levers lose some energy through friction, bending, and other forms of resistance.