vitamin D

any of several fat-soluble vitamins that are essential for increased absorption of calcium and phosphorus from the intestinal tract, found in fish-liver oils, milk, egg yolk, etc. or produced by irradiation of provitamins; specif.,: a deficiency of vitamin D tends to cause rickets

3. , CHOH, produced by irradiation of a derivative of ergosterol
4. , CHOH, produced by irradiation of a derivative of sitosterol