[ ri-duhk-shuh n ]
/ rɪˈdʌk ʃən /


Origin of reduction

1475–85; earlier reduccion < Middle French reduction < Latin reductiōn- (stem of reductiō) a bringing back, equivalent to reduct(us) (past participle of redūcere; see reduce) + -iōn- -ion


Example sentences from the Web for reduction

British Dictionary definitions for reduction

/ (rɪˈdʌkʃən) /


the act or process or an instance of reducing
the state or condition of being reduced
the amount by which something is reduced
a form of an original resulting from a reducing process, such as a copy on a smaller scale
a simplified form, such as an orchestral score arranged for piano
  1. the process of converting a fraction into its decimal form
  2. the process of dividing out the common factors in the numerator and denominator of a fraction; cancellation

Derived forms of reduction

reductive, adjective

Medical definitions for reduction

[ rĭ-dŭkshən ]


Other words from reduction

re•duction•al adj.

Scientific definitions for reduction

[ rĭ-dŭkshən ]

The changing of a fraction into a simpler form, especially by dividing the numerator and denominator by a common factor. For example, the fraction 812 can be reduced to 46, which can be further reduced to 23, in each case by dividing both the numerator and denominator by 2.
A chemical reaction in which an atom or ion gains electrons, thus undergoing a decrease in valence. If an iron atom having a valence of +3 gains an electron, the valence decreases to +2. Compare oxidation.


Beginning students of chemistry are understandably puzzled by the term reduction: shouldn't a reduced atom or ion be one that loses electrons rather than gains them? The reason for the apparent contradiction comes from the early days of chemistry, where reduction and its counterpart, oxidation, were terms invented to describe reactions in which one substance lost an oxygen atom and the other substance gained it. In a reaction such as that between two molecules of hydrogen (2H2) and one of oxygen (O2) combining to produce two molecules of water (2H2O), the hydrogen atoms have gained oxygen atoms and were said to have become “oxidized,” while the oxygen atoms have (as it were) lost them by attaching themselves to the hydrogens, and were said to have become “reduced.” Importantly, though, in the process of gaining an oxygen atom, the hydrogen atoms have had to give up their electrons and share them with the oxygen atoms, while the oxygen atoms have gained electrons. Thus comes the apparent paradox that the “reduced” oxygen has in fact gained something, namely electrons. Today the terms oxidation and reduction are used of any reaction, not just one involving oxygen, where electrons are (respectively) lost or gained.

Cultural definitions for reduction


Any chemical reaction in which the atoms in a material take on electrons.

notes for reduction

Reduction is the opposite of oxidation.