Disaccharides

When two simple sugars combine they're called a disaccharide. Sucrose is made of a unit glucose and a unit of fructose. Maltose is a combination of 2 units of glucose. Lactose is made of glucose and galactose. Most disaccharides are easily broken down by digestion into monosaccharides and then used for energy. A few are indigestible and become "roughage" in our system, though they do provide food to our beneficial intestinal bacteria. An oligosaccharide is a combination of two to ten sugar molecules.

Note that some consider disaccharides to be oligosaccharides...there's not agreement on the nomenclature.