Vitamin D is called:

Vitamin $D$ is called calciferol or ergocalciferol. lt is a steroid hormone that has long been known for its important role in regulating body levels of calcium and phosphorus, and in mineralization of bone.
Vitamin $D$ in human body exist in two form :
(I) Vitamin $D_2$, also called as ergocalciferol.
(II) Vitamin $D_3$, also called as calciferol or cholecalciferol.