A vitamin is an organic molecule (or a group of chemically closely related molecules, i.e., vitamers) that is an essential micronutrient required in small amounts for the proper functioning of an organism’s metabolism.
Essential nutrients cannot be synthesized by the organism at all, or cannot be synthesized in sufficient quantities, and therefore must be obtained through diet.
Source: Wikipedia
Retinol – Vitamin A
Thiamine – Vitamin B1
Cobalamins – Vitamin B12
Riboflavin – Vitamin B2
Niacin – Vitamin B3
Pantothenic Acid – Vitamin B5
Pyridoxine – Vitamin B6
Biotin – Vitamin B7
Folic Acid – Vitamin B9
Ascorbic Acid – Vitamin C
Calciferol – Vitamin D
Tocopherol – Vitamin E
Phylloquinone / Phytor – Vitamin K
