What is the difference between a coupling and a joint?

Basically the difference is that in coupling there cannot be a relative motion between the two links ex:- two shafts coupled in a transmission both will rotate at almost same rpm , where as in a joint its just a joint between two links and there can be a relative motion between the links. ex:- connecting rod and crank in an IC engine where there can be relative motion between the two which are connected by crank pin. read more

mechanical coupling can be called as a mechanical device which is used to connect two mechanical links as well as transmit power between them. mechanical joint is just used to joint two linkages . there is no power or torque transmission between them . read more