A bearing is a machine element that constrains relative motion to only the desired motion, and reduces friction between moving parts. The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fixed axis; or, it may prevent a Swing Bearings motion by controlling the vectors of normal forces that bear on the moving parts. Most bearings facilitate the desired motion by minimizing friction. Bearings are classified broadly according to the type of operation, the motions allowed, or to the directions of the loads (forces) applied to the parts.

Bearings reduce friction between two objects, which allows moving parts to run smoother. Bearings are divided into two main categories: thrust bearings and radial bearings. Thrust bearings support axial loads, which are parallel to the axis of rotation, while radial bearings support turning shafts perpendicular to the axis of rotation. Depending on the application, there is a wide range of bearings to choose from. Common types of bearings include ball bearings, split bearings, and roller bearings. Bearings are also SKF 6003 Bearing available in mounted, unmounted, and flange styles. Ball bearings are the most common type of bearing and are used in applications requiring support of smaller loads. Split bearings are ideal for hard-to-reach places and quick installation while roller bearings are suitable for heavier loads. Roller bearings are generally available in three styles: tapered roller bearings, cylindrical roller bearings, and spherical roller bearings. Key elements to consider when selecting bearings are outer diameter and the shaft diameter the bearing will fit.