U

Ulcer
An area of tissue erosion, for example, of the skin or lining of the gastrointestinal (GI) tract.

Unsaturated fat
A fat that is liquid at room temperature and comes from a plant such as olive, peanut, corn, cottonseed, sunflower, safflower, or soybean. Unsaturated fats tend to lower the level of cholesterol in the blood.