Metamerism

n.
  1. (Biol.) The symmetry of a metameric structure; serial symmetry; the state of being made up of metameres.
  2. (Chem.) The state or quality of being metameric; isomerism due to different bonding patterns in two substances having the same molecular formula. Contrasted with steroisomerism or optical isomerism. Also, the relation or condition of metameric compounds.