reduction

American  

[ri-duhk-shuhn] / rɪˈdʌk ʃən /

noun

• reductions
  plural

1. the act of reducing or the state of being reduced.

2. the amount by which something is reduced or diminished.

3. a form produced by reducing a copy on a smaller scale.

4. Cell Biology. meiosis, especially the first meiotic cell division in which the chromosome number is reduced by half.

5. Chemistry. the process or result of reducing.

6. Movies. the process of making a print of a narrower gauge from a print of a wider gauge.

   the reduction of 35-millimeter films to 16-millimeter films for the school market.

7. a village or settlement of Indians in South America established and governed by Spanish Jesuit missionaries.

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reduction British  

/ rɪˈdʌkʃən /

noun

1. the act or process or an instance of reducing

2. the state or condition of being reduced

3. the amount by which something is reduced

4. a form of an original resulting from a reducing process, such as a copy on a smaller scale

5. a simplified form, such as an orchestral score arranged for piano

6. maths

   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

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reduction Scientific  

/ rĭ-dŭk′shən /

1. The changing of a fraction into a simpler form, especially by dividing the numerator and denominator by a common factor. For example, the fraction 8/12 can be reduced to 4/6, which can be further reduced to 2/3, in each case by dividing both the numerator and denominator by 2.

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.

3. Compare oxidation

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reduction Cultural  

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

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Usage

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.

Discover More

Reduction is the opposite of oxidation.

Other Word Forms

Derived Forms

• nonreduction
  noun
• overreduction
  noun
• self-reduction
  noun
• antireduction
  adjective
• nonreductional
  adjective
• proreduction
  adjective
• reductional
  adjective
• reductive
  adjective

Inflected Forms

Nouns

• reductions
  plural

Etymology

Origin of reduction

First recorded in 1475–85; earlier reduccion, from Middle French reduction, from Latin reductiōn- (stem of reductiō ) “a bringing back,” equivalent to reduct(us) (past participle of redūcere “to lead back” ) + -iōn- noun suffix; see reduce, -ion

Explanation

Reduction is the act of cutting back or making smaller, like the reduction of a school budget that makes it necessary to eliminate art and music programs. The process of reducing something is reduction, or making it smaller. You can talk about a reduction of sugar in someone's diet or a reduction of prices at your favorite shoe store. In math, reduction means bringing fractions to their lowest common denominators. And, in cooking, a reduction is a thick sauce that's made by boiling away most of the liquid, or reducing it to its concentrated essence.

Example Sentences

See Examples For:

reduction reductions

But for Miller, that reduction is still not enough, said sources not authorized to speak publicly about internal matters.

From Los Angeles Times ● Sep. 9, 2026

That long-term reduction may help explain why fossils of the species are relatively uncommon and why the cats may have become increasingly vulnerable to extinction.

From Science Daily ● Sep. 8, 2026

The company said the drug worked across patient subgroups, with a 43% reduction for those with the highest level of disease exacerbations, and a 23% decline for those with milder forms.

From The Wall Street Journal ● Sep. 8, 2026

That, combined with a slowdown in the Chinese economy and a reduction in sales overall, has made China a much more difficult market for European brands.

From BBC ● Sep. 7, 2026

The AEC chairman could not imagine how a bifurcated weapons program would operate or how the reduction in responsibility for the Super would affect morale on the New Mexico mesa.

From "Big Science" by Michael Hiltzik

Data centers, which require enormous amounts of power, could also see substantial reductions in energy use, potentially leading to significant climate benefits.

From Science Daily ● Sep. 11, 2026

The latest specific reductions vary slightly by country.

From BBC ● Sep. 1, 2026

From January to July 2025, for example, registered local enterprises received 147 million yuan in tax reductions and exemptions.

From Barron's ● Aug. 31, 2026

In May, the beauty company launched a test to gauge consumer sensitivity to price reductions, after reporting slower-than-expected sales growth at its own brand during its March quarter.

From The Wall Street Journal ● Aug. 31, 2026

The Chicago Tribune made fare reductions a crusade and openly attacked the railroads.

From "The Devil in the White City" by Erik Larson

Related Words

• contraction
• cut
• cutback
• devaluation
• discount
• rebate