Merriam-Webster Logo
  • Dictionary
  • Thesaurus
  • Scrabble
  • Spanish Central
  • Learner's Dictionary


noun de·duc·tion \di-ˈdək-shən, dē-\

Simple Definition of deduction

  • : the act of taking away something (such as an amount of money) from a total

  • : something (such as an amount of money) that is or can be subtracted from a total

  • : the act or process of using logic or reason to form a conclusion or opinion about something : the act or process of deducing something

Source: Merriam-Webster's Learner's Dictionary

Full Definition of deduction

  1. 1 a :  an act of taking away <deduction of legitimate business expenses> b :  something that is or may be subtracted <deductions from his taxable income>

  2. 2 a :  the deriving of a conclusion by reasoning; specifically :  inference in which the conclusion about particulars follows necessarily from general or universal premises — compare induction b :  a conclusion reached by logical deduction

Examples of deduction in a sentence

  1. The government is offering new tax deductions for small businesses.

  2. What is your pay after the deductions have been taken out?

  3. His guess was based on intuition rather than deduction.

  4. Our deduction was based on the information given to us at the time.

  5. It was a logical deduction.

15th Century

First Known Use of deduction

15th century

DEDUCTION Defined for Kids


noun de·duc·tion \di-ˈdək-shən\

Definition of deduction for Students

  1. 1 :  subtraction

  2. 2 :  an amount deducted

  3. 3 :  a conclusion reached by reasoning <Her deduction was based on all the clues.>

Law Dictionary


noun de·duc·tion

Legal Definition of deduction

  1. 1 :  an amount allowed by tax laws to be subtracted from income in order to decrease the amount of income tax due — see also Internal Revenue Code — compare credit, exclusion, exemption business deduction :  a deduction usually taken from gross income that is allowed for losses or expenses attributable to business activities or to activities engaged in for profit charitable deduction :  a deduction allowed for a contribution to a charity usually that is qualified under the tax law (as sections 170 and 2055 of the Internal Revenue Code) dependency deduction :  a deduction allowed to be taken in a set amount for a qualified dependent (as under sections 151 and 152 of the Internal Revenue Code) itemized deduction :  a deduction for a specifically recorded item that is allowed to be taken from adjusted gross income if the total of such deductions exceeds the standard deduction marital deduction 1 :  a deduction allowed under the Internal Revenue Code to be taken from the gross estate that amounts to the value of any property interest which is included in the estate and which was given by a decedent to the surviving spouse provided that the interest is not terminable during the life of the survivor 2 :  a deduction allowed under the Internal Revenue Code of the value of any gift inter vivos subject to gift tax by one spouse to the other personal deduction :  a deduction allowed to be taken for losses or expenses that are not necessarily attributable to a business activity or an activity engaged in for profit personal exemption deduction :  a deduction for an amount set by tax law that under section 151 of the Internal Revenue Code includes the dependency deduction standard deduction :  a deduction of an amount set by tax law that is allowed to be taken from adjusted gross income unless the taxpayer elects to itemize deductions

  2. 2 in the civil law of Louisiana :  an item of property or an amount that an heir has a right to take from the mass of the succession before any of it is partitioned (as for a debt owed by the deceased to the heir)

Seen and Heard

What made you want to look up deduction? Please tell us where you read or heard it (including the quote, if possible).


to manage or play awkwardly

Get Word of the Day daily email!


Take a 3-minute break and test your skills!


Which of these is a synonym of nonplus?

perplex reduce disapprove soothe
Name That Thing

Test your visual vocabulary with our 10-question challenge!


Test Your Knowledge - and learn some interesting things along the way.