#clutch.coupler  a coupling that connects or disconnects driving and driven parts of a driving mechanism
  supertype:  #coupler__coupling  a mechanical device that serves to connect the ends of adjacent objects
  subtype:  #friction_clutch  a clutch in which one part turns the other by the friction between them
  part of:  #transmission_system
  part:  #clutch_pedal__clutch  a pedal that operates a clutch

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