mechanism consisting of a device that works on mechanical principles

link together

a coupler shaped like the letter U with holes through each end so a bolt or pin can pass through the holes to complete the coupling; used to attach a drawbar to a plow or wagon or trailer etc.

a coupling that connects or disconnects driving and driven parts of a driving mechanism

an automotive power coupling

a coupling (as in a chain) that has one end that turns on a headed pin

an oblong metal coupling with a swivel at one end and an internal thread at the other into which a threaded rod can be screwed in order to form a unit that can be adjusted for length or tension