Carbohydrates can exist in two forms; either chain or ring. When in ring form, only two specific confirmations are stable enough to exist in the body for significant periods of time. One of these forms is called a furanose, used to classify cyclized monosaccharide with 5 ring members. The name derives from the monosaccharide's similarity to the simple molecule furan, a 5 member ring. When naming ringed carbohydrates, the furanose status is included. For example, the carbohydrate ribose when cyclized as a 5 member ring in the alpha confirmation is labeled α-D-Ribofuranose. Significant, widely known molecules that make use of furanoses include RNA.