Ingredient

The term “ingredient” is synonymous with a “substance.” A substance is a matter of constant composition best characterized by the entities (molecules, formula units, atoms) it is composed of and by its physical properties such as density, refractive index, electric conductivity, melting point, etc. (i.e., intentionally used substances, intentional reaction products, impurities). Ingredients are commonly identified by a single Chemical Abstract Services Registry Number (CASRN).