A sugar is any of several simple, water-soluble carbohydrates, which are sweet to the taste. Sugars have the general formula (C_x(H₂O)_y) and are classified as monosaccharides or disaccharides.

 

Monosaccharides or "simple sugars", such as glucose, are used by organisms as a source of energy at the cellular level. Dissacharides, such as sucrose, maltose, and lactose, consist of two monosaccharide units held together by a glycosidic bond.

 

If sucrose is accorded an arbitrary sweetness of 100, then glucose scores 74, fructose 173, lactose 16, maltose 33, xylose 40 (compare saccharin 55,000). The sweetness is correlated with their solubility.