Real Dictionary

vitamin
Vitamins are substances that you need in order to remain healthy, which are found in food or can be eaten in the form of pills.

vitamin in American English
any of a number of unrelated, complex organic substances found variously in most foods, or sometimes synthesized in the body, and essential, in small amounts, for the regulation of the metabolism and normal growth and functioning of the body
noun: any of a group of organic substances essential in small quantities to normal metabolism, found in minute amounts in natural foodstuffs or sometimes produced synthetically: deficiencies of vitamins produce specific disorders

vitamin in British English
noun: any of a group of substances that are essential, in small quantities, for the normal functioning of metabolism in the body. They cannot usually be synthesized in the body but they occur naturally in certain foods: insufficient supply of any particular vit