Reduction is a term that has many meanings and applications in science, technology, medicine, arts, philosophy, and more. It can refer to a process of simplifying, transforming, or reducing something, or a method or technique for achieving a goal or effect. Definition of reduction noun in Oxford Advanced Learner's Dictionary. Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more. The percentage reduction formula is used to compare the decay in two quantities with different initial values. The percentage decrease formula is the ratio of the reduction in the quantity to its initial value multiplied by 100. Definition of Reduction in the Definitions.net dictionary. Meaning of Reduction . What does Reduction mean? Information and translations of Reduction in the most comprehensive dictionary definitions resource on the web.