[dih-duhk-shuh n]


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).

Nearby words

  1. dedolomitize,
  2. deduce,
  3. deduct,
  4. deductible,
  5. deductible clause,
  6. deduction theorem,
  7. deductive,
  8. deductively,
  9. deduplicate,
  10. dedéagach

Origin of deduction

1400–50; late Middle English deduccioun (< Anglo-French) < Latin dēductiōn- (stem of dēductiō) a leading away. See deduct, -ion

Related formsnon·de·duc·tion, nounpre·de·duc·tion, noun

Can be confuseddeduction extrapolation induction generalization hypothesis Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for deduction

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 typeCompare 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

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

Science definitions for deduction



The process of reasoning from the general to the specific, in which a conclusion follows necessarily from the premises.
A conclusion reached by this process.


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.

Culture definitions for deduction


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.