The commodity chemical definition is aligned with as published in ZDHC performance in check guidelines, which means single substances or chemical compounds whose chemical structure is well-known, and their use is to create conditions for a process (such as acid, alkaline, oxidizing, reducing, solubilizing conditions).
They are produced in high volumes with low prices and do not have a brand name but are known by their common chemical names (for example, Acetic Acid). The chemical structure and purity of two commodity chemicals produced by different manufacturers can be the same and can be interchangeable. They are generally sold on technical specifications (such as purity) and are not designed for a unique/special property or effect nor require any scientific research in their development. Usually, commodity chemicals either get reacted in the process (for example Sodium Hydroxide or Sodium Hydrosulphite) or remain in the effluent after the process (for example Common Salt or Glauber’s Salt used in reactive dyeing of cotton)
You can refer to the H2H guideline for more details, even the ZDHC performance in check guideline is also provided there.