acidity /asid″itē/ [L, acidus, sour] , 1. the degree of sourness, sharpness of taste, or ability of a chemical to yield hydrogen ions in an aqueous solution. 2. the degree of gastric acid in the stomach. The acidity varies during any 24-hour period, but the pH averages 0.9 to 1.5. The main source of stomach acidity is hydrochloric acid secreted by the gastric glands of the stomach.
