deduction

American  

[dih-duhk-shuhn] / dɪˈdʌk ʃən /

noun

deductions plural

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.

3. the act or process of deducing.

4. something that is deduced.

   His astute deduction was worthy of Sherlock Holmes.

5. Logic.

   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.

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deduction British  

/ dɪˈdʌkʃən /

noun

1. the act or process of deducting or subtracting

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

3. 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

4. logic

   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

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deduction Scientific  

/ dĭ-dŭk′shən /

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.

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deduction ¹ Cultural  

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

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deduction ² Cultural  

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

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Usage

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.

Other Word Forms

Derived Forms

• nondeduction
  noun
• prededuction
  noun

Inflected Forms

Nouns

• deductions
  plural

Etymology

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

Explanation

If you get a tax deduction it means you get to reduce the amount of your income that is subject to tax. If something's on sale, you might get a percentage deduction from the original price. Deduction means taking away, or an amount taken away. If you're a fan of Sherlock Holmes, you already know that the process of logical deduction helps to solve crimes––you take away the information you do know to deduce the answer to what you don't. In figure skating, every mistake on the ice results in a point deduction––the judges take points away.

Example Sentences

Vermeer eschewed easy narrative deduction, Mr. Graham-Dixon writes, by substituting the map with a blank wall.

From The Wall Street Journal • Jun. 26, 2026

Yet in a strange twist, winning that game means Hull must sell players before the end of the month to avoid a potential points deduction in the Premier League.

From BBC • Jun. 17, 2026

Leicester City provide the precedent for Hull to receive the deduction in the top flight.

From BBC • Jun. 17, 2026

Peter Thiel’s Founders Fund launched “Mafia the Game,” a video series featuring Silicon Valley billionaires playing the social deduction game.

From The Wall Street Journal • Jun. 15, 2026

Logical deduction works fine for the world of ideas.

From "Words Like Loaded Pistols" by Sam Leith

Related Words

• abatement
• allowance
• credit
• discount
• rebate
• reduction
• tax write-off
• write-off