Individual #tribology  the branch of engineering that deals with the interaction of surfaces in relative motion (as in bearings or gears): their design and friction and wear and lubrication
  >part of:  mechanical_engineering  the branch of engineering that deals with the design and construction and operation of machinery
     >part of:  engineering_science__engineeringscience__engineering__applied_science__appliedscience__technology  the discipline dealing with the art or science of applying scientific knowledge to practical problems; "he had trouble deciding which branch of engineering to study"

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