noun

• The act, process, or result of reducing.
• The amount or rate by which something is reduced, e.g. in price.
• (chemistry) A reaction in which electrons are gained and valence is reduced; often by the removal of oxygen or the addition of hydrogen.
• (cooking) The process of rapidly boiling a sauce to concentrate it.
• (mathematics) The rewriting of an expression into a simpler form.
• (computability theory) a transformation of one problem into another problem, such as mapping reduction or polynomial reduction.
• (music) An arrangement for a far smaller number of parties, e.g. a keyboard solo based on a full opera.
• (philosophy, phenomenology) A philosophical procedure intended to reveal the objects of consciousness as pure phenomena. (See phenomenological reduction.)
• (medicine) A medical procedure to restore a fracture or dislocation to the correct alignment, usually with a closed approach but sometimes with an open approach (surgery).
• (paying) A reduced price of something by a fraction or decimal.
• (metalworking) The ratio of a material's change in thickness compared to its thickness prior to forging and/or rolling.