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 and a posteriori are terms that are used especially in logic and philosophy. A priori is from Latin ā priōrī, which means literally, "from what is earlier." A priori knowledge is knowledge that comes from the power of reasoning based on self-evident truths; a priori usually describes lines of reasoning or arguments that proceed from the general to the particular, or from causes to effects. A posteriori is from Latin ā posteriōrī, which means literally, "from what is later." It describes knowledge based solely on experience or personal observation. So, for example, "Every apple is a fruit" is an a priori statement, since it shows simple logical reasoning and isn't a statement of fact about a specific case; "apples are sweet" is a posteriori, as it expresses something the speaker knows from experience.

Examples of a priori in a Sentence

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 And this abstractness of Mr. Wilson is part of a curiously a priori metaphysical idealism. Dan McLaughlin, National Review, 6 Feb. 2024 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

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 18 Jun. 2024.

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