Oxidation is a chemical process in which a substance loses electrons, undergoes an increase in oxidation state, or experiences an increase in the number of oxygen atoms or other electronegative elements. It often involves the addition of oxygen or the removal of hydrogen. Oxidation reactions are essential in various chemical and biological processes. In the context of redox reactions, where reduction accompanies oxidation, the substance being oxidized is referred to as the reducing agent. Common examples include the rusting of iron and the combustion of fuels, where substances lose electrons and exhibit changes in their chemical properties.