- In mathematics, reduction is the process of manipulating a series of equations or matrix into a desired 'simpler' format.
- 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 one phenomenon in terms of another.
- In linguistics, reduction is to shorten the pronounciation of a word. e.g. wanna, lemme, gimme.