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

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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

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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

See Examples For:

deduction deductions

The IRS lets homeowners take a $40,000 tax deduction on their state and local taxes.

From MarketWatch ● Oct. 8, 2026

They were also handed a four-point deduction for this season.

From BBC ● Oct. 7, 2026

The likely punishment is uncertain but, according to Premier League rules, City could face a substantial points deduction, a fine or even expulsion from the top division.

From Barron's ● Oct. 1, 2026

This would take the deduction rates, which currently range from 25% to 30%, to 100% on new projects, according to a report from BMO Capital Markets.

From The Wall Street Journal ● Sep. 28, 2026

Penelope paced the slippery floor in deep concentration, for her powers of deduction were at full throttle.

From "The Hidden Gallery" by Maryrose Wood

No sanction has yet been announced but City could face substantial points deductions, a fine or even expulsion from the Premier League.

From Barron's ● Oct. 9, 2026

The sanctions for City have not yet been decided but potential punishments include expulsion from the league, points deductions and fines.

From BBC ● Oct. 2, 2026

Scholarships with payments up to the cost of tuition, room and board, and academic expenses would be deductions.

From The Wall Street Journal ● Sep. 30, 2026

In this case, your income before deductions would be roughly $142,000 — your $108,000 salary plus your $34,000 of taxable Social Security — before adding any taxable pension or IRA income.

From MarketWatch ● Sep. 30, 2026

She began to talk, pulling deductions from the top of her head.

From "The Mark of Athena" by Rick Riordan

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