Presents the nomenclature common to flexible couplings as used in mechanical power transmission drives. It was prepared to reduce the language barriers that arise between designers, manufacturers, and users when attempting to designate various types of flexible couplngs and their elements. It does not address nomenclature for flexible shafts, quill shafts, universal joints or devices which exhibit slip such as clutches, fluid couplings, magnetic couplings or torque converters.