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

However, should they fail in their appeal, City could face a significant points deduction or, in the most extreme scenario, expulsion from the Premier League.

From BBC ● Nov. 8, 2026

Saltburn's second XI have also been relegated from Division Two and will start the 2027 season in Division Three with a 60-point deduction.

From BBC ● Nov. 6, 2026

The new income ranges for each tax bracket and a higher standard deduction mean that someone who earns the same income next year would likely owe slightly less in taxes.

From The Wall Street Journal ● Nov. 5, 2026

The 2025 law prevented tax rates from rising and it increased the amount of the standard deduction, among other things.

From MarketWatch ● Nov. 5, 2026

It wasn’t exactly foolproof logic, but Emma was pretty sure she could make a deduction: Mom wasn’t on a business trip at all.

From "The Strangers" by Margaret Peterson Haddix

According to the bankruptcy filing, he receives a total monthly income of $59,512.44 but only nets $3,610.31 a month after payroll deductions and expenses.

From Los Angeles Times ● Nov. 6, 2026

That said, the IRS has released its new income-tax brackets for the 2027 tax year, and Andrew Keshner explains what the changes to deductions and other tax breaks could mean for your money.

From MarketWatch ● Nov. 6, 2026

Most filers save money by taking the standard deduction instead of itemizing deductions.

From The Wall Street Journal ● Nov. 5, 2026

To maximize overall deductions, some taxpayers will find it pays to switch back and forth from standard to itemized in different years, and to “bunch” deductions into years when they’re itemizing.

From The Wall Street Journal ● Oct. 30, 2026

Holmes did this by watching Watson’s face and the things he was staring at and making deductions.

From "The London Eye Mystery" by Siobhan Dowd

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