What is the relationship between reduction and oxidation in a chemical reaction?

The relationship between reduction and oxidation in a chemical reaction is that they are complementary processes that are defined in relation to each other. Reduction involves the gain of electrons or a decrease in oxidation state, while oxidation involves the loss of electrons or an increase in oxidation state. When one substance undergoes oxidation, another must undergo reduction, which is why they are often referred to collectively as redox reactions. Hence, stating that reduction is the opposite of oxidation accurately captures the interdependent nature of these two processes, highlighting the fact that they cannot occur in isolation from one another. This principle is foundational in understanding how chemical reactions proceed, particularly in biochemical processes and electrochemical cells.