A nutrient that the body needs in small amounts to function and stay healthy. Sources of vitamins are plant and animal food products and dietary supplements. Some vitamins are made in the human body from food products. Vitamins are either fat-soluble (can dissolve in fats and oils) or water-soluble (can dissolve in water). Excess fat-soluble vitamins are stored in the body’s fatty tissue, but excess water-soluble vitamins are removed in the urine. Examples are vitamin A, vitamin C, and vitamin E. OR  organic nutrients essential in trace amounts to the health of animals. Or  Organic substances required in trace amounts for a number of essential biochemical reactions.