A synovial combined, like the neck or hip joint, which a spherical knob or knoblike part of one bone meets into a cavity or socket of another, in order that some degree of rotary movement is possible in almost every direction. Also referred to as enarthrosis.
A joint, as in a mechanical device, that enables rotary motion everywhere through the activity of a ball in a socket. Also referred to as ball joint.
A joint where one section has a rounded end while the after that section has actually a bowl-shaped end, aided by the curved end being fitted to the bowl shape, enabling the first portion to go around an indefinite number of axes which have one common center.