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• assumption
  assumption

  noun

  something taken for granted; a supposition.
• Assumption
  Assumption

  noun

  the taking up of the Virgin Mary (body and soul) into heaven when her earthly life was ended

assumption

American  

[uh-suhmp-shuhn] / əˈsʌmp ʃən /

noun

• assumptions
  plural

1. something taken for granted; a supposition.

   a correct assumption.

   Synonyms:

   theory, postulate, guess, conjecture, hypothesis, presupposition

2. the act of taking for granted or supposing.

   Synonyms:

   presupposition, presumption

3. the act of taking to or upon oneself.

   Synonyms:

   acceptance

4. the act of taking possession of something.

   the assumption of power.

   Synonyms:

   usurpation, appropriation, seizure

5. arrogance; presumption.

   Synonyms:

   gall, forwardness, effrontery

6. the taking over of another's debts or obligations.

7. Ecclesiastical.

   1. (often initial capital letter) the bodily taking up into heaven of the Virgin Mary.

   2. (initial capital letter) a feast commemorating this, celebrated on August 15.

8. Logic. the minor premise of a syllogism.

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assumption ¹ British  

/ əˈsʌmpʃən /

noun

1. the act of taking something for granted or something that is taken for granted

2. an assuming of power or possession of something

3. arrogance; presumption

4. logic a statement that is used as the premise of a particular argument but may not be otherwise accepted Compare axiom

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Assumption ² British  

/ əˈsʌmpʃən /

noun

1. the taking up of the Virgin Mary (body and soul) into heaven when her earthly life was ended

2. the feast commemorating this, celebrated by Roman Catholics on Aug 15

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Pop Culture

—Assumption persona: A persona is a detailed description of a fictional user (of a product, software program, etc.), based on real-world data. Software engineers and data companies create personas as user models to help build their products. In order to illustrate the utility of using data-driven personas in design, “assumption personas” (personas derived from existing assumptions about users) are used as negative examples showing how assumptions can lead to bad design choices. —Assumption of risk: the name for a defense used in tort law, where the defense argues that the plaintiff took action knowing the risks involved.

Other Word Forms

Derived Forms

• misassumption
  noun
• nonassumption
  noun
• overassumption
  noun
• preassumption
  noun
• reassumption
  noun
• self-assumption
  noun
• superassumption
  noun
• assumptive
  adjective
• assumptively
  adverb

Inflected Forms

Nouns

• assumptions
  plural

Etymology

Origin of assumption

First recorded in 1250–1300; Middle English assumpcioun, assompcioun, assumsion, from Latin assūmptiōn- (stem of assūmptiō ), equivalent to assūmpt(us) “taken up” (past participle of assūmere ) + -iōn- noun suffix; see origin at assume, -ion

Explanation

An assumption is something that you assume to be the case, even without proof. For example, people might make the assumption that you're a nerd if you wear glasses, even though that's not true. Or very nice. From the Latin assumptionem, meaning “a taking or receiving,” assumption was recorded circa 1300 as a noun describing “the reception of the Virgin Mary into heaven.” The word later shook its religious roots and developed into the noun we hear more often today, usually when a person takes something for granted or literally takes possession of something.

Example Sentences

See Examples For:

assumption Assumption assumptions

The simplest assumption is that beyond our cosmic horizon, there is simply more universe.

From Science Daily ● Sep. 28, 2026

And my assumption is that part of the reason you got into this race is that you were beginning to see signs that that was not going to hold.

From Slate ● Sep. 28, 2026

There is also the touching assumption that someone is in charge—good, regular people who’ll take care of things.

From The Wall Street Journal ● Sep. 24, 2026

But that assumption took a hit one night in 2018 after a violent hailstorm.

From BBC ● Sep. 23, 2026

We should operate on the assumption that Ridge arrived safely and wasn’t hit by anything.

From "The First State of Being" by Erin Entrada Kelly

The sanctuary of the Lavra’s Assumption Cathedral sustained a direct hit.

From The Wall Street Journal ● Jun. 15, 2026

Ms. O'Grady received a bachelor's degree in English from Assumption College and an M.B.A. in financial management from Pace University.

From The Wall Street Journal ● Feb. 8, 2026

Canan has been part of Chesney’s staff for more than a decade, starting at Assumption College in 2014 before later following Chesney to Holy Cross, James Madison and now UCLA.

From Los Angeles Times ● Jan. 2, 2026

Assumption Island, in the western Indian Ocean, possesses little at first glance that would set even the most curious and intrepid traveller's pulse racing.

From BBC ● Sep. 25, 2025

One Sunday in March, she arrived at Assumption before the Divine Liturgy had started.

From "Middlesex: A Novel" by Jeffrey Eugenides

The results get particularly interesting—with failure rates as high as 85.4%—when we alter the baseline assumptions.

From The Wall Street Journal ● Sep. 30, 2026

That also means confronting one of the industry’s most persistent assumptions: that a successful chef must sacrifice everything else to the job.

From Salon ● Sep. 27, 2026

One experiment found people had warmer, more engaged interactions with robots that made social flubs, including “judgmental mistakes, wrong assumptions, expressing tiredness or boredom, or getting overexcited.”

From Slate ● Sep. 27, 2026

Two years later, new scientific evidence came to light which challenged one of the key assumptions underpinning the prosecution case.

From BBC ● Sep. 25, 2026

Putting the two assumptions together, we conclude that the average toy block in this collection has the interesting property of having three inches to a side and a volume of sixty-three cubic inches!

From "Innumeracy: Mathematical Illiteracy and Its Consequences" by John Allen Paulos

Related Words

• acceptance
• belief
• expectation
• guess
• hunch
• hypothesis
• inference
• premise
• presumption
• supposition
• suspicion
• theory