The conversion of a substrate into a particular product, irrespective of reagents or mechanisms involved. For example, the transformation of aniline (C₆H₅NH₂) into N-phenylacetamide (C₆H₅NHCOCH₃) may be effected by use of acetyl chloride or acetic anhydride or ketene. A transformation is distinct from a reaction, the full description of which would state or imply all the reactants and all the products.