: a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena
the wave theory of light
: a belief, policy, or procedure proposed or followed as the basis of action
her method is based on the theory that all children want to learn
: an ideal or hypothetical set of facts, principles, or circumstances —often used in the phrase in theory
in theory, we have always advocated freedom for all
: a hypothesis assumed for the sake of argument or investigation
: an unproved assumption : conjecture
: a body of theorems presenting a concise systematic view of a subject
theory of equations
: the analysis of a set of facts in their relation to one another
The immune surveillance theory of cancer holds that in a way we all do have cancer, that a healthy immune system fights off rogue cells as they appear. —Sallie Tisdale, Harper's, June 2007 The family's theory was that the cheating businessmen somehow framed their brother. —Eliza Griswold, Harper's, September 2006 The theory of the teacher with all these immigrant kids was that if you spoke English loudly enough they would eventually understand. —E. L. Doctorow, Loon Lake, (1979) 1980 While strolling around, we kept the run of the moon all the time, and we still kept an eye on her after we got back to the hotel portico. I had a theory that the gravitation of refraction, being subsidiary to atmospheric compensation, the refrangibility of the earth's surface would emphasize this effect in regions where great mountain ranges occur, and possibly so even-handed impact the odic and idyllic forces together, the one upon the other, as to prevent the moon from rising higher than 12,200 feet above sea-level. This daring theory had been received with frantic scorn by some of my fellow-scientists, and with an eager silence by others. —Mark Twain, A Tramp Abroad, 1880 a widely accepted scientific theory Her method is based on the theory that all children want to learn. There are a number of different theories about the cause of the disease. She proposed a theory of her own. Investigators rejected the theory that the death was accidental. There is no evidence to support such a theory. He is a specialist in film theory and criticism. See More
Recent Examples on the Web Furthering that theory, UC guard Dan Skillings posted a video to TikTok Sunday, claiming the team wrapped up its last workout in Under Armour gear. —Victoria Moorwood, The Enquirer, 1 May 2023 Professor Chris Klausmeier, a mathematician and theoretical ecologist at MSU, incorporated Dr. Twardochleb’s observations with his own theory. —Maureen Mackey, Fox News, 30 Apr. 2023 One theory, advanced by Eric Roesch, an expert in environmental impact analyses, is that obtaining approval to build it from the US Army Corps of Engineers would require months or years that SpaceX didn’t want to spend. —Tim Fernholz, Quartz, 24 Apr. 2023 One theory, that the flash was caused by a falling U.S. satellite, was ruled out by the U.S. space agency NASA. —Reuters, NBC News, 20 Apr. 2023 Christopher Nolan loves a wild, existential theory. —Leena Kim, Town & Country, 18 Apr. 2023 John Lin is living with his wife, Mei Lin, who is a college professor, and son, Eddy Lin, who is a student studying music theory. —Benj Edwards, Ars Technica, 11 Apr. 2023 The theory, if true, underscores Michelangelo’s outsize ego, or at least his cheeky sense of humor. —Kelly Crow, wsj.com, 19 Apr. 2023 The group is the only global non-government organization of its kind, dedicated to promoting the application of theory, methodology and scientific techniques to the conservation of the architectural and archaeological heritage. —Arlyssa D. Becenti, The Arizona Republic, 17 Apr. 2023 See More
These examples are programmatically compiled from various online sources to illustrate current usage of the word 'theory.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
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