THEORY Synonyms: 35 Similar and Opposite Words

Q: How does the noun 'theory' differ from other similar words?

The words hypothesis and law are common synonyms of theory . While all three words mean "a formula derived by inference from scientific data that explains a principle operating in nature," theory implies a greater range of evidence and greater likelihood of truth. // the theory of evolution

Q: When would 'hypothesis' be a good substitute for 'theory'?

Although the words hypothesis and theory have much in common, hypothesis implies insufficient evidence to provide more than a tentative explanation. // a hypothesis explaining the extinction of the dinosaurs

Q: When might 'law' be a better fit than 'theory'?

The meanings of law and theory largely overlap; however, law implies a statement of order and relation in nature that has been found to be invariable under the same conditions. // the law of gravitation

theory

noun

ˈthē-ə-rē

Definition of theory

as in hypothesis

an idea that is the starting point for making a case or conducting an investigation set out to prove her theory that people can't really taste any difference between colas, so they buy according to the product's image

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How does the noun theory differ from other similar words?

The words hypothesis and law are common synonyms of theory. While all three words mean "a formula derived by inference from scientific data that explains a principle operating in nature," theory implies a greater range of evidence and greater likelihood of truth.

the theory of evolution

When would hypothesis be a good substitute for theory?

Although the words hypothesis and theory have much in common, hypothesis implies insufficient evidence to provide more than a tentative explanation.

a hypothesis explaining the extinction of the dinosaurs

When might law be a better fit than theory?

The meanings of law and theory largely overlap; however, law implies a statement of order and relation in nature that has been found to be invariable under the same conditions.

the law of gravitation

Example Sentences

Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.

Recent Examples of theory Having watched supposedly secure systems fail has given many an irreverence for authority and an impatience with grand theories. — Harry Booth, Time, 20 Oct. 2026 One theory suggests Phobos and Deimos formed from debris produced by a massive impact involving Mars. — Muskan Bhatia, Interesting Engineering, 20 Oct. 2026 Before Daly, scientists had been leaning toward theories that involved Earth's rapid spin billions of years ago, when each day may have at one time lasted as little as 2 or 3 hours. — Micah Hanks, Space.com, 19 Oct. 2026 The collective anxiety that was palpable moments earlier melted away, as many saw the speech as another attempt to revive disproved theories unlikely to be taken seriously by most voters. — Andy Mannix, ProPublica, 19 Oct. 2026 See All Example Sentences for theory

Recent Examples of Synonyms for theory

Noun

Consistent with their hypothesis, the secretion signal helps transfer the enzyme out of the cell, while the lipid anchor holds it near the cell surface.

— Muskan Bhatia, Interesting Engineering, 21 Oct. 2026
But there are indirect consequences of the Many Worlds hypothesis that could lend the idea credibility.

— Philipp Strasberg, Scientific American, 20 Oct. 2026

Definition of hypothesis

Noun

Michael Monaghan, portfolio manager at Founder ETFs, says that's part of the investment thesis.

— Jordan Novet, CNBC, 26 Oct. 2026
Written in Latin, the theses were relatively tentative in tone, consisting of 95 short propositions—most just a sentence or two.

— Encyclopedia Britannica, Encyclopedia Britannica, 22 Oct. 2026

Definition of thesis

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“Theory.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/theory. Accessed 28 Oct. 2026.

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