Tribology:  noun: the branch of science and technology concerned with surfaces in relative motion, as in bearings. Derivatives: tribological adjective tribologist noun.  Origin: from Greek tribos ‘rubbing’. (Oxford English Dictionary).

Tribology: noun: the science and technology of interacting surfaces in relative motion, including the study of friction, lubrication and wear.  Origin: mid 20th C.  [Coined from tribo- + -ology]. (Encarta World English Dictionary).

Tribology concerns: abrasion, abrasive wear, adhesion, adhesive wear, wear failure of gears, bearings, bearing design and technology, bevel gears, ceramics, condition monitoring of machinery, contact fatigue, contact mechanics, design audits, elastohydrodynamic lubrication, engineering analysis, epicyclic gears, erosion, failure analysis, fatigue failures, fatigue, fluid film lubrication, fracture, friction and wear, gear failures, gears, gearboxes, heat treatment, helical gears, herringbone gears, human artificial joints, hypoid gears, impact, impact wear, internal gears lubricants, manufacturing, materials, metals, metalworking, polymers, seals, service environment, spur gears, stress rupture, surface properties and characterization, thermal fatigue, tooth bending fatigue, tribological systems, wear, worm gears.