Individual #mechanical_engineering  the branch of engineering that deals with the design and construction and operation of machinery
  >part:  #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:  #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"

No statement uses or specializes #mechanical_engineering; click here to add one.