One of the articular processes of a vertebra, of which there are usually four, two superior and two inferior.

So called because it is a "bony offshoot" that connects one bone to another (as in the zygapophyseal joint). "Yoke" historically refers to a bar or frame by which two oxen or other draught animals are joined at their necks enabling them to pull a cart, plough, etc.; (by extension) a device attached to a single draught animal for the same purpose.