ETYM Latin frictio, from fricare, frictum,to rub: cf. French friction. Related to Fray to rub, arid cf. Dentifrice.
In physics, the force that opposes the relative motion of two bodies in contact. The coefficient of friction is the ratio of the force required to achieve this relative motion to the force pressing the two bodies together.
Friction is greatly reduced by the use of lubricants such as oil, grease, and graphite. Air bearings are now used to minimize friction in high-speed rotational machinery. In other instances friction is deliberately increased by making the surfaces rough —for example, brake linings, driving belts, soles of shoes, and tires.
1. Effort expended in rubbing one object against another; SYN. detrition, rubbing.
2. The resistance encountered when one body is moved in contact with another; SYN. rubbing.