Lubrication occurs when opposing surfaces are completely separated by a lubricant film. The applied load is carried by pressure generated within the fluid, and frictional resistance to motion arises entirely from the shearing of the viscous fluid. The science of friction, lubrication and wear is called tribology. Lubrication is classified into three major categories:

1. Hydrodynamic lubrication (HL)
2. Elastohydrodynamic lubrication (EHL or EHD)
3. Boundary lubrication

See also

• Bearing (mechanical)
• Grease (lubricant)
• Motor oil

Lubrikation