Sugar is a generic term for sweet-tasting, soluble carbohydrates. It mainly refers to simple sugars called monosaccharides (such as glucose, fructose, and galactose) and compound sugars called disaccharides (such as sucrose, lactose, and maltose). The most common sugar is sucrose, which is made of one glucose molecule bonded to one fructose molecule and is the white crystalline sugar commonly used as a sweetener in food and beverages. Sugars are found naturally in many plants, fruits, and dairy products, and they provide a major source of energy for the body by being converted into glucose.