n [ME, fr. OE hring; akin to OHGr hring ring] (before 12c) A polymeric structure resulting from the reaction of one end of a molecule with the other end, forming a ring structure that may be likened to a snake biting its own tail. The stability of ring molecules formed from carbon–carbon chains is generally greatest in five- to six-membered rings, and least in 9- to 11-membered rings. The probability of ring formation decreases rapidly as the length of the molecule increases. Thus the presence of a few small rings in the polymer is usually insignificant.