An epiphyseal line is an epiphyseal plate that has become ossified.
[1] The process of it forming from an epiphyseal plate is named epiphyseal closure.
[2] In adult humans, it marks the point of fusion between the epiphysis and the metaphysis.
[3][4] The epiphyseal line serves no function in the bone, being purely vestigial.
However, it serves as an indicator of the boundary between the epiphysis and diaphysis.