A coupling is a mechanical element part that connects two shafts together to accurately transmit the power from the drive side to the driven side while absorbing the mounting error (misalignment), etc. of the two shafts.
Coupling in the machine industry is interpreted as “a part that connects two shafts together”, and is generally called “coupling”, “shaft coupling” or “joint”.
Power can be transmitted by using a coupling, even between axes of different diameters