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