vitamin - any of a group of organic substances essential in small quantities to normal metabolism

B complex, B vitamin, B-complex vitamin, vitamin B, vitamin B complex, B - originally thought to be a single vitamin but now separated into several B vitamins

bioflavinoid, citrin, vitamin P - a vitamin that maintains the resistance of cell and capillary walls to permeation

ascorbic acid, vitamin C - a vitamin found in fresh fruits (especially citrus fruits) and vegetables; prevents scurvy