#coupler__coupling  a mechanical device that serves to connect the ends of adjacent objects
  supertype:  #mechanical_device  mechanism consisting of a device that works on mechanical principles
  subtype:  #clevis  a coupling to attach a drawbar to a plow or wagon or trailer etc.
  subtype:  #clutch.coupler  a coupling that connects or disconnects driving and driven parts of a driving mechanism
     subtype:  #friction_clutch  a clutch in which one part turns the other by the friction between them
        subtype:  #cone_clutch__cone_friction_clutch  a friction clutch in which the frictional surfaces are cone-shaped
        subtype:  #disk_clutch  a friction clutch in which the frictional surfaces are disks
        subtype:  #slip_clutch__slip_friction_clutch  a friction clutch that will slip with the torque is too great
  subtype:  #fluid_drive__fluiddrive  an automotive power coupling
  subtype:  #swivel  a coupling (as in a chain) that has one end that turns on a headed pin
  subtype:  #universal_joint__universaljoint__universal  coupling that connects two rotating shafts allowing freedom of movement in all directions; "in motor vehicles a universal joint allows the driveshaft to move up and down as the vehicle passes over bumps"

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