[ dih-duhk-shuhn ]
See synonyms for deduction on
  1. the act or process of deducting; subtraction.

  2. something that is or may be deducted: She took deductions for a home office and other business expenses from her taxes.

  1. the act or process of deducing.

  2. something that is deduced: His astute deduction was worthy of Sherlock Holmes.

  3. Logic.

    • a process of reasoning in which a conclusion follows necessarily from the premises presented, so that the conclusion cannot be false if the premises are true.

    • a conclusion reached by this process.: Compare induction (def. 4).

Origin of deduction

First recorded in 1400–50; late Middle English deduccioun, from Anglo-French, from Latin dēductiōn-, stem of dēductiō “a leading away”; see deduct, -ion

Other words from deduction

  • non·de·duc·tion, noun
  • pre·de·duc·tion, noun

Words that may be confused with deduction

Words Nearby deduction Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use deduction in a sentence

British Dictionary definitions for deduction


/ (dɪˈdʌkʃən) /

  1. the act or process of deducting or subtracting

  2. something, esp a sum of money, that is or may be deducted

    • the process of reasoning typical of mathematics and logic, whose conclusions follow necessarily from their premises

    • an argument of this type

    • the conclusion of such an argument

  1. logic

    • a systematic method of deriving conclusions that cannot be false when the premises are true, esp one amenable to formalization and study by the science of logic

    • an argument of this type: Compare induction (def. 4)

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for deduction


[ dĭ-dŭkshən ]

  1. The process of reasoning from the general to the specific, in which a conclusion follows necessarily from the premises.

  2. A conclusion reached by this process.

usage For deduction

The logical processes known as deduction and induction work in opposite ways. In deduction general principles are applied to specific instances. Thus, using a mathematical formula to figure the volume of air that can be contained in a gymnasium is applying deduction. Similarly, applying a law of physics to predict the outcome of an experiment is reasoning by deduction. By contrast, induction makes generalizations based on a number of specific instances. The observation of hundreds of examples in which a certain chemical kills plants might prompt the inductive conclusion that the chemical is toxic to all plants. Inductive generalizations are often revised as more examples are studied and more facts are known. If certain plants that have not been tested turn out to be unaffected by the chemical, the conclusion about the chemical's toxicity must be revised or restricted. In this way, an inductive generalization is much like a hypothesis.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for deduction (1 of 2)


A process of reasoning that moves from the general to the specific. (Compare induction.)


A cost or expense subtracted from revenue, usually for tax purposes.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.