theoretical
Americanadjective
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of, relating to, or consisting in theory; not practical (distinguished from applied).
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existing only in theory; hypothetical.
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given to, forming, or dealing with theories; speculative.
adjective
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of or based on theory
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lacking practical application or actual existence; hypothetical
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using or dealing in theory; impractical
Other Word Forms
Etymology
Origin of theoretical
First recorded in 1610–20; theoretic, from Late Latin theōrēticus, from Greek theōrētikós, equivalent to theōrēt(ós) “to be seen” (verbal adjective derived from theōreîn “to view”) + -ikos -ic; see -al 1
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Explanation
Something theoretical is concerned with theories and hypotheses — it's not necessarily based on real life or meant to be applied to real life. Theoretical things are based on theory and ideas, while practical ones are based on practice. Theoretical thinking can be really helpful when you're trying to imagine something or problem-solve, but your theories should always be tested out in the practical world. As philosopher Bertrand Russell said, “The theoretical understanding of the world, which is the aim of philosophy, is not a matter of great practical importance to animals, or to savages, or even to most civilized men.”
Vocabulary lists containing theoretical
Albert Einstein
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Theoretical models had predicted that the molecule could exist in two equally likely structures.
From Science Daily • Apr. 7, 2026
Theoretical physicists have pointed out fatal flaws in Mr. White’s reasoning and researchers at the Dresden University of Technology failed to replicate some of his results.
From The Wall Street Journal • Mar. 20, 2026
"The electrons must occupy very specific states -- so-called doorway states," explains Prof. Florian Libisch from the Institute for Theoretical Physics.
From Science Daily • Nov. 4, 2025
Narlikar stayed in the UK till 1971 as a Fellow at King's College and a founding member of the Institute of Theoretical Astronomy.
From BBC • May 23, 2025
The only groups that didn’t run numbers based on testing worked in the small Theoretical and Physical Research Division and the Stability Research Division—the “no-air” engineers.
From "Hidden Figures" by Margot Lee Shetterly
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
