(n.) A body or compound which is isomeric with another body or compound; a member of an isomeric series.

acid acidity agent alkali alkalinity alloisomer anion antacid artificial isotope atom base biochemical cation chemical chemical element chromoisomer compound copolymer deuterium dimer element heavy chemicals heavy hydrogen high polymer homopolymer hydracid inorganic chemical ion isobar isotone isotope macromolecule metamer molecule monomer neutralizer nonacid nuclear isomer organic chemical oxyacid polymer protium pseudoisomer radical radioactive isotope radioisotope reagent strontium 90 sulfacid trimer