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[dih-duhk-shuh n] /dɪˈdʌk ʃən/
the act or process of deducting; subtraction.
something that is or may be deducted:
She took deductions for a home office and other business expenses from her taxes.
the act or process of deducing.
something that is deduced:
His astute deduction was worthy of Sherlock Holmes.
  1. 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.
  2. a conclusion reached by this process.
    Compare induction (def 4).
Origin of deduction
late Middle English
1400-50; late Middle English deduccioun (< Anglo-French) < Latin dēductiōn- (stem of dēductiō) a leading away. See deduct, -ion
Related forms
nondeduction, noun
prededuction, noun
Can be confused Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for deduction
Contemporary Examples
Historical Examples
  • Intellectually I may make mistakes in deduction, but spiritually I cannot but find God.

  • I'll give about eight thousand with a deduction on account of the glades.

    Master and Man Leo Tolstoy
  • His art is less for every deduction from his holiness, and less for every defect of common sense.

    Essays, First Series Ralph Waldo Emerson
  • That is not a matter of opinion, not a matter of inference or deduction.

    The Life of Cesare Borgia Raphael Sabatini
  • My deduction is that those signals did not and could not cause the explosion.

    The Destroyer Burton Egbert Stevenson
British Dictionary definitions for deduction


the act or process of deducting or subtracting
something, esp a sum of money, that is or may be deducted
  1. the process of reasoning typical of mathematics and logic, whose conclusions follow necessarily from their premises
  2. an argument of this type
  3. the conclusion of such an argument
  1. 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
  2. an argument of this type Compare induction (sense 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
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Word Origin and History for deduction

early 15c., "action of deducting," from Middle French déduction or directly from Latin deductionem (nominative deductio), noun of action from past participle stem of deducere (see deduce). Meaning "that which is deducted" is from 1540s. As a term in logic, from Late Latin use of deductio as a loan-translation of Greek apagoge.

Online Etymology Dictionary, © 2010 Douglas Harper
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deduction in Science
  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.

Our Living Language  : 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 © 2002. Published by Houghton Mifflin. All rights reserved.
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deduction in Culture

deduction definition

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

deduction definition

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

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