One of the articular processes of a vertebra, of which there are usually four, two anterior and two posterior. See under Vertebra.

Greek zygon = yoke, apo = from, physis = growth; the articular process of a vertebra. The downward "growth" of the vertebra above articulates with the upward "growth" of the vertebra below, forming a zygapophyseal joint.

A zygapophysis is a process which sticks out of an end of a vertebra to lock with a zygapophysis on the next vertebra, to make the backbone more stable.