symphysis

From Ancient Greek, via sym- + φύσις (phúsis, “growth”)

symphysis (countable and uncountable, plural symphyses)

1. The process of two originally separate bones growing together as the subject matures, as with the pubic bones or lower jawbones in humans.
2. A line, discernable on an X-ray, showing such fusion.
3. The cartilaginous material that adjoins and facilitates the junction of such bones, with or without synovia.