Kauri-butanol/KB value: measure of the aromatic properties of a solvent, based on its power to dissolve kauri gum; aromatics have high KB values, paraffinic solvents low KB values.

Kinetic/dynamic/sliding friction: the resistance to a force maintaining a relative motion between two surfaces, sliding instead of rolling; varies with surface conditions, surface materials, presence and type of lubricant (see friction).

Kinetic viscosity: value obtained by dividing the absolute viscosity of a fluid by its mass density.