hypothesis

noun
hy·​poth·​e·​sis | \hī-ˈpä-thə-səs \
plural hypotheses\hī-​ˈpä-​thə-​ˌsēz \

Definition of hypothesis 

1a : an assumption or concession made for the sake of argument

b : an interpretation of a practical situation or condition taken as the ground for action

2 : a tentative assumption made in order to draw out and test its logical or empirical consequences

3 : the antecedent clause of a conditional statement

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Choose the Right Synonym for hypothesis

hypothesis, theory, law mean a formula derived by inference from scientific data that explains a principle operating in nature. hypothesis implies insufficient evidence to provide more than a tentative explanation. a hypothesis explaining the extinction of the dinosaurs theory implies a greater range of evidence and greater likelihood of truth. the theory of evolution 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

The Difference Between Hypothesis and Theory

A hypothesis is an assumption, an idea that is proposed for the sake of argument so that it can be tested to see if it might be true.

In the scientific method, the hypothesis is constructed before any applicable research has been done, apart from a basic background review. You ask a question, read up on what has been studied before, and then form a hypothesis.

A hypothesis is usually tentative; it's an assumption or suggestion made strictly for the objective of being tested.

A theory, in contrast, is a principle that has been formed as an attempt to explain things that have already been substantiated by data. It is used in the names of a number of principles accepted in the scientific community, such as the Big Bang Theory. Because of the rigors of experimentation and control, it is understood to be more likely to be true than a hypothesis is.

In non-scientific use, however, hypothesis and theory are often used interchangeably to mean simply an idea, speculation, or hunch, with theory being the more common choice.

Since this casual use does away with the distinctions upheld by the scientific community, hypothesis and theory are prone to being wrongly interpreted even when they are encountered in scientific contexts—or at least, contexts that allude to scientific study without making the critical distinction that scientists employ when weighing hypotheses and theories.

The most common occurrence is when theory is interpreted—and sometimes even gleefully seized upon—to mean something having less truth value than other scientific principles. (The word law applies to principles so firmly established that they are almost never questioned, such as the law of gravity.)

This mistake is one of projection: since we use theory in general to mean something lightly speculated, then it's implied that scientists must be talking about the same level of uncertainty when they use theory to refer to their well-tested and reasoned principles.

The distinction has come to the forefront particularly on occasions when the content of science curricula in schools has been challenged—notably, when a school board in Georgia put stickers on textbooks stating that evolution was "a theory, not a fact, regarding the origin of living things." As Kenneth R. Miller, a cell biologist at Brown University, has said, a theory "doesn’t mean a hunch or a guess. A theory is a system of explanations that ties together a whole bunch of facts. It not only explains those facts, but predicts what you ought to find from other observations and experiments.”

While theories are never completely infallible, they form the basis of scientific reasoning because, as Miller said "to the best of our ability, we’ve tested them, and they’ve held up."

Examples of hypothesis in a Sentence

In contrast to Bingham's hypothesis that Machu Picchu was the birthplace of the first Inca and the hearth area of the Inca civilization, current scholars believe that the city was built as a country estate … — Roger Balm, Focus On Geography, Spring 2004 Campus veterans marvel at all the poolside apartments that have sprung up since Georgia popped the income cap off its merit awards. Professors are testing their hypothesis that instead of increasing college enrollment, the state's $1.7 billion scholarship program has been a blessing for the automobile industry—since so many families roll the savings into buying new cars. — Greg Winter, New York Times, 31 Oct. 2002 Isaac Newton initially argued against a parabolic orbit for the … comet of 1680, preferring the hypothesis of two independent comets, one for the inbound and one for the outbound leg. However, Newton later showed that the orbit of the comet could indeed be fit by a parabola. — Daniel C. Boice and Walter Huebner, "Physics and Chemistry of Comets," in Encyclopedia of the Solar System Paul R. Weissman et al., editors1999 As stated, our working hypothesis suggests a straightforward way to look for evidence that would confirm or disconfirm it: can you predict what is omitted and what is included in alphabetic representations? — Timothy Shopen and Joseph M. Williams, Standards and Dialects in English, 1980 Other chemists rejected his hypothesis. Their hypothesis is that watching excessive amounts of television reduces a person's ability to concentrate. The results of the experiment did not support his hypothesis.
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Recent Examples on the Web

Kristensen's hypothesis uses math to ask a familiar question: What if investigators have been looking in the wrong place the whole time? Sam Blum, Popular Mechanics, "New Research Might Locate Flight MH370—And Solve One of the Greatest Aviation Mysteries of All Time," 7 Dec. 2018 My father and others have been speaking about the environment for decades - not basing it on fallacy or new-age hypothesis, but rooted in science and facts, and the sobering awareness of our environmental vulnerability. Caroline Hallemann, Town & Country, "Prince Harry Just Paid Tribute to Prince Charles and His Work in the Fight Against Climate Change," 26 Oct. 2018 This groundbreaking hypothesis led to the theory of quantum mechanics, which also had no need for aether. Meg Neal, Popular Mechanics, "The Eternal Quest for Aether, the Cosmic Stuff That Never Was," 19 Oct. 2018 Going with the crowd To provide a test of this hypothesis, the researchers ran a little experiment with more than 550 people via Amazon’s paid Mechanical Turk service. Scott K. Johnson, Ars Technica, "You think your neighbors can drive energy conservation," 18 Sep. 2018 Another popular hypothesis that explains humans’ fondness of nature is the attention restoration theory. Ben Tobin, USA TODAY, "Desk, swivel chair, trees: Why companies are moving the office outdoors," 28 June 2018 The risk of receiving a diagnosis of diabetes was also lower among fasters, although that had not been our primary hypothesis. SELF, "What You Need to Know Before Trying Intermittent Fasting," 7 Nov. 2018 The results are helping fill in details of her hypothesis that the moon was formed from a stew of gaseous rock surrounding the early earth—and solve a 50-year-old mystery. Joe Barrett, WSJ, "MacArthur ‘Genius Grant’ Winners Include Sci-Fi Junkie and an MIT Economist," 4 Oct. 2018 His hypothesis is that moving out of the city is based on a number of factors: employment, housing, education, and concerns about safety and gun violence are the ones that leap out at him. Patrick Sisson, Curbed, "How a ‘reverse Great Migration’ is reshaping U.S. cities," 31 July 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'hypothesis.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of hypothesis

1641, in the meaning defined at sense 1a

History and Etymology for hypothesis

Greek, from hypotithenai to put under, suppose, from hypo- + tithenai to put — more at do

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Last Updated

18 Dec 2018

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Time Traveler for hypothesis

The first known use of hypothesis was in 1641

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More Definitions for hypothesis

hypothesis

noun

English Language Learners Definition of hypothesis

: an idea or theory that is not proven but that leads to further study or discussion

hypothesis

noun
hy·​poth·​e·​sis | \hī-ˈpä-thə-səs \
plural hypotheses\-​ə-​ˌsēz \

Kids Definition of hypothesis

: something not proved but assumed to be true for purposes of argument or further study or investigation

hypothesis

noun
hy·​poth·​e·​sis | \hī-ˈpäth-ə-səs \
plural hypotheses\-​ˌsēz \

Medical Definition of hypothesis 

: a proposition tentatively assumed in order to draw out its logical or empirical consequences and test its consistency with facts that are known or may be determined it appears, then, to be a condition of the most genuinely scientific hypothesis that it be…of such a nature as to be either proved or disproved by comparison with observed facts— J. S. Mill

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