a priori


a pri·​o·​ri ˌä-prē-ˈȯr-ē How to pronounce a priori (audio)
ˌā-(ˌ)prī-ˈȯr-ˌī How to pronounce a priori (audio)
: relating to or derived by reasoning from self-evident propositions compare a posteriori
: presupposed by experience
: being without examination or analysis : presumptive
: formed or conceived beforehand
a priori adverb
ˌā-(ˌ)prī-ˈȯr- How to pronounce a priori (audio)

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A priori, Latin for "from the former", is traditionally contrasted with a posteriori. The term usually describes lines of reasoning or arguments that proceed from the general to the particular, or from causes to effects. Whereas a posteriori knowledge is knowledge based solely on experience or personal observation, a priori knowledge is knowledge that comes from the power of reasoning based on self-evident truths. So, for example, "Every mother has had a child" is an a priori statement, since it shows simple logical reasoning and isn't a statement of fact about a specific case (such as "This woman is the mother of five children") that the speaker knew about from experience.

Example Sentences

There's no a priori reason to think your expenses will remain the same in a new city. an a priori argument for the defendant's innocence
Recent Examples on the Web Pushing certain values as a priori can backfire. Arielle Pardes, Wired, 9 Sep. 2021 My point is that, a priori, there is no reason to assume a beneficial effect of this kind of stimulation. Neuroskeptic, Discover Magazine, 21 July 2019 For instance, grant applications, and requests for ethical approval, already contain detailed a priori protocols in most cases. Neuroskeptic, Discover Magazine, 23 Sep. 2012 But more fundamentally this most egalitarian of faiths on a priori grounds has perpetuated one of the least egalitarian traditions of the past 10,000 years down to the modern period. Razib Khan, Discover Magazine, 19 Mar. 2012 Smart contracts allow creating communication protocols that do not require a priori trust between parties. David Balaban, Forbes, 11 Feb. 2023 The problem is when it is passed off as being a priori. Neuroskeptic, Discover Magazine, 14 Apr. 2012 In-group variation rarely leads to a re-consideration of a priori categories and studies with negative results do not get the same space, in journals or in the press... Neuroskeptic, Discover Magazine, 15 July 2017 If evolution is not taken as an a priori, then these evidences are far less compelling. Carl Zimmer, Discover Magazine, 22 July 2012 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'a priori.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


borrowed from Medieval Latin ā priōrī literally, "from what is earlier"

First Known Use

1652, in the meaning defined at sense 1a

Time Traveler
The first known use of a priori was in 1652

Dictionary Entries Near a priori

Cite this Entry

“A priori.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/a%20priori. Accessed 1 Jun. 2023.

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