Bearing is a part of a machine that supports or guides a moving part. Bearings hold weight, turn with the motion of other parts, and reduce friction and wear by enabling sliding or rotating parts to move smoothly. Bearings are used in a wide variety of machines, including automobile engines, conveyors, elevators, generators, and turbines. They are often classified according to their function. For example, linear bearings guide objects along a track. Journal bearings keep a journal (shaft) turning smoothly.