ˌsiˌnäˈstōsə̇s noun
also syn·os·te·osis (ˌ)siˌnästēˈosəs, səˌn-
( plural synosto·ses also synoste·oses -ōˌsēz)
Etymology: synostosis, New Latin, from syn- + -ostosis; synosteosis, New Latin, from syn- + oste- + -osis
: union of two or more separate bones to form a single bone ; also : the union so formed (as at an epiphyseal line) — compare ankylosis