Zygapophysis

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.

Each typical vertebra has 4 of them: two front (prezygapophysis) and two back (postzygapophysis), two left and two right. Its plural is "zygapophyses".

Its origin is Greek ζυγον = "yoke" (because it links two vertebrae) + απο = "away" + φυσις = "process".