Carbohydrates can exist in two forms; either chain or ring. When in ring form, only two specific configurations are stable enough to exist in the body for significant periods of time. One of these forms is called a pyranose, used to classify cyclized monosaccharide with 6 ring members. The name derives from the monosaccharide's similarity to the simple molecule pyran, a 6 member ring. When naming ringed carbohydrates, the pyranose status is included. For example, the carbohydrate glucose when cyclized as a 6 member ring in the alpha confirmation is labeled α-D-Glucopyranose. Pyranoses in terms of chemical stability are preferred to furanoses, and if able to a chain molecule will cyclize into a pyranose more often than a furanose.