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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. 2015.
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Examples from the web for deduction
  • Through the logical deduction of how, an understanding arises.
  • In addition, it will end charity car donation since the voucher would far exceed the tax deduction.
  • They are able to express logical thought, and demonstrate simple deduction at about age 2.
  • But in trying to avert a minor deduction, she would end up paying a major price.
  • Provided you have no other gains, you can take your $3000 deduction for your losses.
  • Darwin is all about induction while physics is about deduction.
  • The author nicely balances action and deduction in a mystery that works as a political thriller as well as a historical whodunit.
  • The software helps you make sure you're taking advantage of every business deduction and write-off.
  • You have to get everything right to avoid a deduction.
  • Observation followed by deduction is standard practice in science.
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 American Heritage® 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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