deduction

[dih-duhk-shuhn]

noun

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.

deduction

/ 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

deduction

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.

deduction

¹

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

deduction

²

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

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

• nondeduction noun
• prededuction noun

Word History and Origins

Origin of deduction¹

First recorded in 1400–50; late Middle English deduccioun, from Anglo-French, from Latin dēductiōn-, stem of dēductiō “a leading away”; deduct, -ion

Example Sentences

“The combined ordinary taxable income from the Roth conversion, taxable interest, and nonqualified dividends of $47,500 is completely wiped out by the total available deductions,” they said.

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The new temporary deductions for tips, overtime, car loan interest and for seniors aren’t indexed for inflation.

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The IRS announced inflation adjustments for 2026 tax brackets, increasing the standard deduction to $16,100 for individuals and $32,200 for married couples.

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The law prevented income-tax rates from increasing as had been scheduled under the tax-code overhaul he signed into law in 2017, and it introduced a range of new temporary tax deductions.

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Despite its partial closure amid the government shutdown, the Internal Revenue Service on Thursday released details of its 2026 tax brackets and the dollar value of the standard deduction.

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Related Words

• abatement 
• allowance 
• credit 
• discount 
• rebate 
• reduction 
• tax write-off www.thesaurus.com
• write-off