theory

[ thee-uh-ree, theer-ee ]

/ ˈθi ə ri, ˈθɪər i /

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See synonyms for: theory / theories on Thesaurus.com

noun, plural the·o·ries.

a coherent group of tested general propositions, commonly regarded as correct, that can be used as principles of explanation and prediction for a class of phenomena: Einstein's theory of relativity.

a proposed explanation whose status is still conjectural and subject to experimentation, in contrast to well-established propositions that are regarded as reporting matters of actual fact.

Mathematics. a body of principles, theorems, or the like, belonging to one subject: number theory.

the branch of a science or art that deals with its principles or methods, as distinguished from its practice: music theory.

a particular conception or view of something to be done or of the method of doing it; a system of rules or principles: conflicting theories of how children best learn to read.

contemplation or speculation: the theory that there is life on other planets.

guess or conjecture: My theory is that he never stops to think words have consequences.

OTHER WORDS FOR theory

1 principle, law, doctrine.

2 idea, notion, concept, postulate, thesis.

6 thought, opinion, judgment, conclusion, deduction, view.

7 hypothesis, surmise, supposition, presumption.

See synonyms for theory on Thesaurus.com

QUIZ

CAN YOU ANSWER THESE COMMON GRAMMAR DEBATES?

There are grammar debates that never die; and the ones highlighted in the questions in this quiz are sure to rile everyone up once again. Do you know how to answer the questions that cause some of the greatest grammar debates?

Question 1 of 7

Which sentence is correct?

His boss, whom he admires, is waiting to meet with him about the big project.

His boss, who he admires, is waiting to meet with him about the big project.

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Idioms about theory

in theory, ideally; hypothetically: In theory, mapping the human genome may lead to thousands of cures.

Origin of theory

First recorded in 1590–1600; from Late Latin theōria, from Greek theōría “a viewing, contemplating,” equivalent to theōr(eîn) “to view” + -ia noun suffix; see -y³

synonym study for theory

1, 2. In technical or scientific use, Theory, principle, and law represent established, evidence-based explanations accounting for currently known facts or phenomena or for historically verified experience: the theory of relativity, the germ theory of disease, the law of supply and demand, the principle of conservation of energy. Often the word law is used in reference to scientific facts that can be reduced to a mathematical formula: Newton's laws of motion. In these contexts the terms theory and law often appear in well-established, fixed phrases and are not interchangeable. In both technical and nontechnical contexts, theory can also be synonymous with hypothesis, a conjecture put forth as a possible explanation of phenomena or relations, serving as a basis for thoughtful discussion and subsequent collection of data or engagement in scientific experimentation in order to rule out alternative explanations and reach the truth. In these contexts of early speculation, the words theory and hypothesis are often substitutable for one another: Remember, this idea is only a theory/hypothesis; Pasteur's experiments helped prove the theory/hypothesis that germs cause disease. Obviously, certain theories that start out as hypothetical eventually receive enough supportive data and scientific findings to become established, verified explanations. Although they retain the term theory in their names, they have evolved from mere conjecture to scientifically accepted fact.

WORDS THAT MAY BE CONFUSED WITH theory

hypothesis, law, theory (see synonym study at the current entry)

Words nearby theory

theoretics, The Orient, Origin of Species, The, theorist, theorize, theory, theory-laden, theory of equations, Theory of Everything, theory of games, theory of mind

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use theory in a sentence

“Our prosecutors have all too often inserted themselves into the political process based on the flimsiest of legal theories,” Barr went on.
The stunning hypocrisy of Bill Barr|Andrew Prokop|September 17, 2020|Vox
Turn Wilson’s mathematical crank, and you get a related theory describing groups of those pieces — perhaps billiard ball molecules.
How Mathematical ‘Hocus-Pocus’ Saved Particle Physics|Charlie Wood|September 17, 2020|Quanta Magazine
She also learns immediately that this theory is “not just incorrect but hateful, like saying that different races had different IQs” — and yet, “in my heart, I knew that Whorf was right,” that language does change the way you think.
The true love story in Elif Batuman’s The Idiot is a love affair with language|Constance Grady|September 11, 2020|Vox
It applies a different random error to each piece of information that’s encoded—which in theory makes it impossible to break without knowing the key.
Quantum computers threaten to end digital security. Here’s what’s being done about it|Jeremy Kahn|September 11, 2020|Fortune

Kindrachuk also works on ebola, and he says over the years many such theories have been put forth in scientific journals without provoking this kind of response.
Wearing a mask could protect you from COVID-19 in more ways than you think|Kat Eschner|September 10, 2020|Popular-Science
But at the heart of this “Truther” conspiracy theory is the idea that “someone” wants to destroy Bill Cosby.
Phylicia Rashad and the Cult of Cosby Truthers|Stereo Williams|January 8, 2015|DAILY BEAST
Is it sort of evidence of the Gladwellian 10,000 hours theory?
Coffee Talk with Fred Armisen: On ‘Portlandia,’ Meeting Obama, and Taylor Swift’s Greatness|Marlow Stern|January 7, 2015|DAILY BEAST
But a 2011 study of genetic evidence from 30 ethnic groups in India disproved this theory.
The Himalayas’ Hidden Aryans|Nina Strochlic|January 3, 2015|DAILY BEAST
But, in theory, that started to change last week with the first meeting of SIX, the State Innovation Exchange.
The Left’s Answer to ALEC|Ben Jacobs|December 15, 2014|DAILY BEAST
So I was happy to see that the European theory of terroir was in action, promoting with pride the qualities of a specific region.
Beer Countries vs. Wine Countries|Clive Irving|December 7, 2014|DAILY BEAST
In the year of misery, of agony and suffering in general he had endured, he had settled upon one theory.
The Homesteader|Oscar Micheaux
Dean Swift was indeed a misanthrope by theory, however he may have made exception to private life.
Gulliver's Travels|Jonathan Swift
The other is the new theory: that the Bible is the work of many men whom God had inspired to speak or write the truth.
God and my Neighbour|Robert Blatchford
The evolution theory alleges that they were evolved, slowly, by natural processes out of previously existing matter.
God and my Neighbour|Robert Blatchford
And our surroundings at that particular moment were not the most favorable to coherent thought or plausible theory-building.
Raw Gold|Bertrand W. Sinclair

British Dictionary definitions for theory

theory

/ (ˈθɪərɪ) /

noun plural -ries

a system of rules, procedures, and assumptions used to produce a result

abstract knowledge or reasoning

a speculative or conjectural view or ideaI have a theory about that

an ideal or hypothetical situation (esp in the phrase in theory)

a set of hypotheses related by logical or mathematical arguments to explain and predict a wide variety of connected phenomena in general termsthe theory of relativity

a nontechnical name for hypothesis (def. 1)

Word Origin for theory

C16: from Late Latin theōria, from Greek: a sight, from theōrein to gaze upon

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for theory

theory

[ thē′ə-rē, thîr′ē ]

A set of statements or principles devised to explain a group of facts or phenomena. Most theories that are accepted by scientists have been repeatedly tested by experiments and can be used to make predictions about natural phenomena. See Note at hypothesis.

Cultural definitions for theory

theory

In science, an explanation or model that covers a substantial group of occurrences in nature and has been confirmed by a substantial number of experiments and observations. A theory is more general and better verified than a hypothesis. (See Big Bang theory, evolution, and relativity.)

theory

OTHER WORDS FOR theory

Idioms about theory

Origin of theory

synonym study for theory

WORDS THAT MAY BE CONFUSED WITH theory

Words nearby theory

Words related to theory

How to use theory in a sentence

British Dictionary definitions for theory

Word Origin for theory

Scientific definitions for theory

Cultural definitions for theory