轴承（bearing）香港人俗称啤令（音译）、**则称培林，机械专有用词；故名思义，是承托转轴(rotating axle)、或直线运动轴(linearly moving shaft)的机件部份，在机械中起到支撑旋转体或直线来回运动体的作用。当其他机件在轴上彼此产生相对运动时，用来保持轴的中心位置及控制该运动的机件，就称之为轴承。其英文造字复数词bearings又可专门解作走珠, 正是绝大部份构成整个轴承，用作可与转轴互相滑动，及使转轴转动时产生的摩擦力减至最低的部件。然而其取义实主要源自其动词to bear「承担、承托」的意思。

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 motion by controlling the vectors of normal forces that bear on the moving parts. Many bearings also facilitate the desired motion as much as possible, such as 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.