as·​sump·​tion | \ə-ˈsəm(p)-shən \

Definition of assumption 

1 : a taking to or upon oneself the assumption of a new position

2 : the act of laying claim to or taking possession of something the assumption of power

3a : an assuming that something is true a mistaken assumption

b : a fact or statement (such as a proposition, axiom (see axiom sense 2), postulate, or notion) taken for granted

4a : the taking up of a person into heaven

b capitalized : August 15 observed in commemoration of the Assumption of the Virgin Mary

5 : the taking over of another's debts

Keep scrolling for more

Examples of assumption in a Sentence

I made the assumption that he was coming, so I was surprised when he didn't show up. He will come home tomorrow. At least, that's my assumption. Many scientific assumptions about Mars were wrong. I'm telling you our arrival time on the assumption that you will check to see whether or not our flight is on time before you come to the airport. Her plan is based on the underlying assumption that the economy will improve in the near future. her assumption of the presidency the buyer's assumption of debt
See More

Recent Examples on the Web

By making the assumption that everyone has options, transportation stereotypes ignore greater equity issues. Alissa Walker, Curbed, "People are not defined by what we use to get around," 27 June 2018 Then the researchers made some assumptions based on probability. Lydia Denworth, Scientific American, "Thanksgiving Dinner May End Sooner If Guests Pass the Gravy across a Partisan Divide," 1 June 2018 When lawyer Aaron Schlossberg threw a fit in front of employees at an eatery in Manhattan, his anger seemed to stem from the assumption that those who spoke Spanish could not possibly belong in America., "7 Women Discuss How They Handle The "Where Are You From?" Question," 23 May 2018 The confusion and concern in January by the board stemmed from assumptions by members that all, or nearly all, of the technology costs for the new HMS were included in the project budget. Chuck Fieldman,, "FCC assistance and lower bids drop technology cost deficit for new Hinsdale Middle School," 17 May 2018 Part of that comes from biblical assumptions that many scholars no longer support. Tara Isabella Burton, Vox, "Conservative evangelical women are calling out a leader’s sexism. It’s a huge moment for #MeToo.," 9 May 2018 Were the inspector general to find evidence of violations of the law, there is a mechanism for charges to be brought — but Gaetz begins from the assumption that laws were broken and then works backward. Philip Bump, Washington Post, "The anti-Trump conspiracy theory, neatly outlined by Trump’s number one cable-news defender," 20 Mar. 2018 In fact, the annual projected return on asset assumption, or ROA, to ensure solvency is only 6.5% for each of these plans. Edward Mckinley, kansascity, "KC union retirees join rally in Ohio for pension fix — or is it a bailout?," 13 July 2018 Constitutionalism is not a mere institutional form but a culture—a set of sentiments, habits and assumptions, a permeating spirit that animates an otherwise lifeless paper scheme. Joseph Tartakovsky, WSJ, "The Culture That Sustains America’s Constitution," 2 July 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'assumption.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of assumption

13th century, in the meaning defined at sense 4a

History and Etymology for assumption

Middle English, from Late Latin assumption-, assumptio taking up, from Latin assumere — see assume

Keep scrolling for more

Learn More about assumption

Share assumption

Statistics for assumption

Last Updated

4 Nov 2018

Look-up Popularity

Time Traveler for assumption

The first known use of assumption was in the 13th century

See more words from the same century

Keep scrolling for more

More Definitions for assumption


as·​sump·​tion | \ə-ˈsəmp-shən \

Kids Definition of assumption

1 : the act of taking on the assumption of power

2 : something accepted as true I'm making plans on the assumption that you will be here.

Keep scrolling for more

Comments on assumption

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


playful or foolish behavior

Get Word of the Day daily email!

Test Your Vocabulary

Autumn Words of the Day 2018

  • a-top-down-image-of-road-through-an-autumn-forest
  • Which is a synonym of fugacious?
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!

Word Winder's CrossWinder

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


Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!