Bearing definition is quite unique. It is described as a device which is responsible for reducing the frictional force between two machinery parts when they are in motion. The movement can be liner or rotational. Based on the motions which are allowed through the bearing, bearings are accordingly manufactured. The principle of operation and the design of the bearings are also dependent on operation or the purpose. Often this motion is described as the directions, where the load is applied.

The most common bearing is the plain bearing which is present. There are two surfaces of contact in such bearings which are rubbed together. There is graphite or oil in such point of contact. By bearing definition, one could well understand that the bearing has inner race and outer race which has a number of ball elements within. Plain bearings have a hole in the middle through which the shaft passes.

Sometimes layer of bearing metal are fused or kept in the form of separable sleeve. Entirely acceptable accuracy can be achieved and that too at minimal cost. Therefore, starting from plain bearings to more complex ball bearing and others are widely used. Nonetheless, there are some operations which can be performed only with the most efficient bearing. In such bearing size and weight have to be accurate. It is also important to keep in mind the cost of the entire machinery.

There are different types of bearing available. According to purpose the principles of operation varies too. According to bearing definition the plain bearings are the simplest and the styles of such plain bearing which are available are rifle bearing, sleeve bearing, journal bearing, bushings, etc.  Other than that there are also roller bearings and ball bearings where rolling element is present. A unique bearing which is used for carried load slightly off the center by rolling the axle is the jewel bearing.

Sometimes bearing also carries load by liquid or gas. These bearings are called fluid bearing. Other than that there are magnetic bearings which are present. At the same time, in some of the bearing the load is supported by means of elements which are capable for bending. Such bearings are called flexure bearings.

By bearing definition, we know that bearings allow two loads in motion to simultaneously move together. The motion can be of different types. The motion can be axial rotation, leaner motion, spherical and hinge. Hinge motions are seen in door while linear motion in the drawer.