Reduction or reducing has several meanings:

• In mathematics, reduction is the process of manipulating a series of equations or matrices into a desired 'simpler' format.

• In computational complexity theory, reduction is the transformation of an instance of one problem into an equivalent instance of another.

• In cooking, reduction is the process of thickening a liquid mixture such as a sauce by evaporation.

• In chemistry, reduction is the reverse of oxidation, i.e. the formal oxidation state of an atom (independent or within a molecule) is reduced by the addition of electrons. A reduced gas is thus hydrogen-rich.

• In philosophy, reduction is the process of explaining a particular phenomenon or subject matter in terms of more fundamental concepts, principles or elements.

• In linguistics, reduction is to shorten the pronunciation of a word. e.g. wanna, lemme, gimme.

• In physiology, reduction or reducing is another name for weight loss or dieting.

• In surgery, reduction is a medical procedure to restore a fracture to a correct alignment.