https://mazziotti.uchicago.edu/qcdictionary/r_terms/reduction_oxidation/index.html Reduction and oxidation (redox) are complementary processes in which one species gains electrons (reduction) and another loses electrons (oxidation). Redox reactions are fundamental in electrochemistry, energy storage, and many biological and inorganic processes; they are often described in terms of oxidation states and half-reactions. Hugo en-us