An oligosaccharide is a
polymer of between 2 and 20 monosaccharides. These are differentiated from
polysaccharides by their large, but limited nature, being medium-sized
carbohydrates. Oligosaccharides are formed through
glycosidic bonds by
hydrolysis of several
monosaccharides. The simplest form of an oligosaccharide is called a
disaccharide.
A quick example of an oligosaccharide (and a disaccharide) is sucrose, aka table sugar.