#sun_gear__sungear  the central gear in a epicyclic train
  supertype:  #gear_wheel__gear__cogwheel  a toothed wheel that engages another toothed mechanism in order to change the speed or direction of transmitted motion
  part of:  #epicyclic_train__epicyclictrain__epicyclic_gear_train  a system of epicyclic gears in which at least one wheel axis itself revolves about another fixed axis

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