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

See Examples For:

deduction deductions

Eleven days later Southampton learned their fate and were thrown out of the play-offs and given a four-point deduction for this season.

From BBC ● Aug. 14, 2026

Congress rewrote the charitable-deduction rules, effective Jan. 1, 2026, with the One Big Beautiful Bill Act, and every change pushed value away from the deduction and toward your adjusted gross income.

From MarketWatch ● Aug. 14, 2026

Inflows amounted to 89 billion kroner after deduction of expenses, it added.

From The Wall Street Journal ● Aug. 12, 2026

I have a handle on Medicare surcharges and the $6,000 senior additional deduction rules.

From MarketWatch ● Aug. 6, 2026

The scientists could determine if plutonium was present only by reading its trace radioactive signature; this was science performed not by observation but by deduction.

From "Big Science" by Michael Hiltzik

They give $15,000 a year, and their other itemized deductions equate to about $12,000.

From MarketWatch ● Aug. 14, 2026

It’s not just work, though, where these deductions are made.

From Los Angeles Times ● Aug. 6, 2026

Ideally, the U.S. would have “universal access” to retirement savings accounts, giving all workers the option of contributing automatically to a savings plan via payroll deductions.

From The Wall Street Journal ● Jun. 27, 2026

In the 1990s, Murrin and her husband used an accountant who cooked up bogus deductions and pocketed a share of the wrongly-inflated tax refunds.

From MarketWatch ● Jun. 25, 2026

“Here’s an itemized schedule of deductions from the year Kennedy was assassinated. Go have it framed!”

From "Miss Peregrine's Home for Peculiar Children" by Ransom Riggs

Related Words

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