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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

Evolutionary theory is no longer heretical, Galileo has been issued a hall pass to heaven, and quite a few sincere if entirely inadequate apologies have been issued, mostly to people long dead.

From Salon • Apr. 5, 2026

One theory believed to be part of the investigation is that the school, next to an Islamic Revolutionary Guards Corps base, could have been hit as a result of outdated intelligence.

From BBC • Apr. 3, 2026

Having a whole country on your knee was weird enough in theory, but it was all kinds of awkward in practice.

From "Chronicles of a Lizard Nobody" by Patrick Ness

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