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
Derived 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.
Yale economist Robert Shiller has been widely credited with laying much of the theoretical groundwork for perpetual futures.
From MarketWatch • Jun. 5, 2026
The paper claimed the first discovery of a Majorana fermion, a theoretical particle central to the tech giant’s quantum computing effort.
From Barron's • Jun. 3, 2026
Google says Willow can solve a theoretical problem in five minutes which would take the world's current fastest super computers 10 septillion - or 10,000,000,000,000,000,000,000,000 - years to complete.
From BBC • May 28, 2026
The lived experience verifies the theoretical, and the theoretical gives those with lived experience tools to understand their own lives.
From Slate • May 27, 2026
Others, like Dorothy Hoover and Doris Cohen, had highly refined understandings of theoretical math, differentiating their way through nested equations ten pages deep with nary an error in sign.
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.
