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Definitions

theory

[thee-uh-ree, theer-ee] / ˈθi ə ri, ˈθɪər i /
NOUN
hypothesis, belief
Synonyms
STRONGEST
approach argument assumption code concept doctrine idea ideology method philosophy plan position premise proposal provision rationale scheme speculation suspicion system thesis understanding
STRONG
base basis codification conditions conjecture dogma feeling foundation grounds guess guesswork hunch impression outlook postulate presentiment presumption shot stab supposal supposition surmise theorem
WEAK
formularization suppose systemization
Antonyms
STRONGEST
disbelief fact information reality truth
STRONG
calculation knowledge measurement proof
WEAK
certainty

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.

That’s good news, on the theory that insiders know more about their companies’ prospects than anyone else.

From MarketWatch • Apr. 6, 2026

One theory was that Ford suffered from tunnel vision.

From Slate • Apr. 6, 2026

Neither of them made any substantive changes to core Roman Catholic doctrine, but when you’re the bishop of Rome and the head of the world’s largest single religious denomination, practice matters more than theory.

From Salon • Apr. 5, 2026

"By combining theory with our experimental ability to precisely control surface terminations, we open a new path toward MXenes with improved stability and tailored functional properties," concludes Ghorbani-Asl.

From Science Daily • Apr. 4, 2026

The rating agencies, in theory, were just such an authority.

From "The Big Short" by Michael Lewis

From Roget's 21st Century Thesaurus, Third Edition Copyright © 2013 by the Philip Lief Group.