Plain bearings are mechanical components charged with bearing a load and allowing a sliding or rotational motion between two parts of a machine. Their main purpose is preventing wear of the points of support of the machine, which would take place if the shafts were to roll directly on the structure.

Sleeve bearings facilitate linear movement between two parts. Sleeve bearings consist of a metal, plastic or fiber-reinforced composite sleeves that reduce vibrations and noise by absorbing friction between two moving parts using a sliding motion.