This glossary defines commonly used lubricant and tribology terms referenced across technical documentation, specifications, standards, and product data sheets. Definitions are descriptive and provided to support consistent interpretation of technical language.
Core terms
Viscosity
Resistance of a fluid to flow at a given temperature.
Kinematic viscosity
Viscosity measured under gravity flow conditions, typically expressed in mm²/s.
Viscosity index
An indicator describing how viscosity changes with temperature.
Base oil
The primary fluid component of a lubricant before additives are introduced.
Additive
A component added to modify or enhance lubricant performance characteristics.
Shear stability
The ability of a lubricant to retain viscosity under mechanical stress.
Oxidation
Chemical reaction between lubricant components and oxygen, typically accelerated by heat.
Foaming
The presence and persistence of air bubbles within a lubricant.
Air release
The tendency of entrained air to separate from a lubricant.
Demulsibility
The ability of a lubricant to separate from water.
Wear protection
A general term describing lubricant properties that reduce surface damage under load.