a posteriori


a pos·​te·​ri·​o·​ri ˌä-(ˌ)pō-ˌstir-ē-ˈȯr-ē How to pronounce a posteriori (audio)
ˌā-(ˌ)pä-ˌstir-ē-ˈȯr-ˌī How to pronounce a posteriori (audio)
: relating to or derived by reasoning from observed facts compare a priori
a posteriori adverb

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A posteriori, Latin for "from the latter", is a term from logic, which usually refers to reasoning that works backward from an effect to its causes. This kind of reasoning can sometimes lead to false conclusions. The fact that sunrise follows the crowing of a rooster, for example, doesn't necessarily mean that the rooster's crowing caused the sun to rise.

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A priori and a posteriori are terms that 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 posteriori in a Sentence

Recent Examples on the Web This a posteriori saga gives us a refreshed Raphael, whose psychological acuity feels newly approachable. Roberta Smith, New York Times, 26 Nov. 2020

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'a posteriori.' 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 posteriōrī literally, "from what is later"

First Known Use

1588, in the meaning defined at sense 1

Time Traveler
The first known use of a posteriori was in 1588

Dictionary Entries Near a posteriori

Cite this Entry

“A posteriori.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/a%20posteriori. Accessed 4 Mar. 2024.

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