Reduction denotes making a thing smaller, simpler, less complex or more fundamental. Although the exact meaning varies by field, each usage involves transforming an entity or process into a reduced form that is easier to handle, explain or conserve. This article surveys common senses, technical definitions and representative examples across disciplines.

Overview

In ordinary language, reduction often means a decrease in quantity, size or intensity: a price reduction, weight reduction, or the reduction of waste. In technical contexts the term usually implies a specific operation that converts one state into another considered simpler, lower-energy, lower-dimensional or more basic. Understanding which sense is intended requires attention to context and discipline-specific conventions.

Chemistry

In chemistry, reduction is a specific type of chemical change: the gain of electrons by an atom, ion or molecule, and the complementary half of a redox process. Reduction alters oxidation states and can change bonding and reactivity. Reagents that donate electrons are called reducing agents. For introductory material on the subject, see chemical reduction. Discussions of electron transfer and the behavior of charged particles are often labelled under electrons, and treatments of affected substances appear under entries for molecules.

Cooking and food preparation

In culinary practice, reduction describes concentrating a liquid mixture—such as stocks, sauces, wine or fruit juices—by evaporating water through simmering or boiling. Reduction intensifies flavor, thickens texture and can change the balance of sweetness and acidity. Techniques include simmering to a desired volume, deglazing pans to recover flavor, and careful timing to avoid over-reduction and bitterness. The result is a sauce or glaze with amplified taste and viscosity.

Philosophy and the sciences

In philosophy and scientific explanation, reduction or reductionism refers to accounts that explain higher-level phenomena in terms of lower-level entities or laws—for example, explaining biological processes in terms of chemistry, or mental states in terms of neural activity. Reduction can be methodological (a research strategy), ontological (a claim about what fundamentally exists), or explanatory (a way to unify theories). Critics emphasize emergence and the autonomy of higher-level descriptions when lower-level accounts are incomplete or impractical.

Linguistics

In linguistics, reduction covers processes that shorten or weaken word forms and sounds in fluent speech. Phonetic reduction can produce contractions and clitic forms (for example, "wanna" or "gonna" in colloquial English), reductions of vowels in unstressed syllables, and variations that affect rhythm and intelligibility. These processes influence accent, tempo and grammaticalization over time.

Medicine and health

In orthopedics, a reduction is the restoration of a dislocated joint or fractured bone to its correct alignment. Closed reduction is performed without opening the skin; open reduction involves surgical exposure and fixation. Timing, technique and post-reduction care affect outcomes and healing. The word reduction is also used informally for weight loss or the deliberate lowering of body mass in health contexts.

History and policy

The term has historical and institutional senses. In parts of South America during the early modern period, Catholic missionaries established settlements known as "reductions" where indigenous communities were gathered and reorganized for religious and administrative purposes. In 17th-century Swedish history, the Reduction refers to policies by which the Crown reclaimed lands previously granted to the nobility; this political measure changed landholding patterns and royal finances.

Environment, consumption and economics

Waste reduction and purchasing reduction focus on preventing material from entering waste streams and lowering consumption. Waste reduction is the top priority in the waste hierarchy (reduce, reuse, recycle) because preventing waste at source saves resources and energy. Purchasing reduction encourages buying fewer or longer-lasting goods to reduce environmental impact and household expenses.

Mathematics and computer science

In mathematics and theoretical computer science, a reduction is a precise transformation that converts one problem or object into another in a way that preserves essential features. Reductions show relative difficulty: if problem A reduces to problem B under an efficient transformation, then an algorithm for B yields a solution for A. Complexity theory uses formal reductions (for example, polynomial-time reductions) to classify problems and identify hardness, such as NP-completeness. Reductions also appear in algebra (simplifying equations), logic (transforming formulas) and algorithm design (mapping new tasks to well-studied ones).

Common features and distinctions

  1. All senses involve a transformation toward a smaller, simpler, or more fundamental form, but differ in means and aims (physical removal of mass, conceptual simplification, or formal transformation).
  2. In chemistry reduction always accompanies oxidation; in explanation, reduction may succeed or fail depending on pragmatic and theoretical constraints.
  3. Practical reductions (cooking, orthopedic procedures, environmental actions) require technique, timing and context to be effective.

Further reading and resources

Introductory treatments and overviews are useful when first approaching a specific sense: chemical and redox introductions (chemical reduction), materials on electron transfer (electrons), general chemistry and molecular descriptions (molecules), discussions of dieting and weight change (weight reduction), and historical studies of Swedish land policy (the Reduction). Because the word spans many disciplines, readers should consult domain-specific sources for technical detail and practice.