CNOH

from The Collaborative International Dictionary of English v.0.48
Polymeric \Pol`y*mer"ic\, a. [Poly- + Gr. ? part.] (Chem.)
   Having the same percentage composition (that is, having the
   same elements united in the same proportion by weight), but
   different molecular weights; -- often used with with; thus,
   cyanic acid ({CNOH}), fulminic acid ({C2N2O2H2}), and
   cyanuric acid ({C3N3O3H3}), are polymeric with each other.
   [1913 Webster]

   Note: The figures expressing the number of atoms of each
         element in a number of polymeric substances are
         respectively multiples and factors of each other, or
         have some simple common divisor. The relation may be
         merely a numerical one, as in the example given above,
         or a chemical one, as in the case of aldehyde,
         paraldehyde, and metaldehyde.
         [1913 Webster]
         [1913 Webster]