a priori
adjective
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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
Chandler Fritz, Harpers Magazine, 20 Aug. 2025
These new loops manufacture demand, legitimacy, and cultural weight—not because of what the content says, but because of how it was engineered a priori.
—Emil Steiner, Forbes.com, 14 Aug. 2025
One of his most significant contributions was introducing new mathematical tools to model and incorporate a priori data—which relies on deductive reasoning to make predictions—to address signal recovery challenges.
—IEEE Spectrum, 3 Oct. 2024
Knowing a priori which stocks will outperform the market is also much more difficult than reviewing the trends that occurred in the past.
—Wayne Winegarden, Forbes, 2 Oct. 2024
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Cite this Entry
“A priori.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/a%20priori. Accessed 31 Oct. 2025.
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