Definition of HYPOTHESIS

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., editors, 1999 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.

Recent Examples on the Web

This hypothesis has been at the core of many Alzheimer’s drug development efforts which have ultimately ended in heart break, including for companies like Eli Lilly, Merck, Roche, and other pharmaceutical giants. — Sy Mukherjee, Fortune, "Biogen's Stock Is Soaring Because of Its Experimental Alzheimer's Drug — But Some Are Urging Caution," 6 July 2018 So now our hypothesis is that the flu in some circumstances can produce an immune reaction that turns wrong, and instead of clearing the flu, is also attacking the hypocretin neurons. — Helen Branswell, STAT, "A stubborn medical mystery: Was pandemic flu vaccine tied to an increase in narcolepsy cases?," 5 July 2018 This hypothesis could be reinforced by bringing back the first pristine samples from carbonaceous asteroids. — Jeremy Hsu, Scientific American, "Japan’s Hayabusa2 Spacecraft Nears Its Target, the Asteroid Ryugu," 26 June 2018 This hypothesis is consistent with the fact that labor force participation has fallen more for workers with lower levels of educational attainment. — N. Gregory Mankiw, New York Times, "Why Aren’t More Men Working?," 15 June 2018 The light fluctuations seen from Icarus make this hypothesis unlikely, the study authors say, because their observations would not have been possible with intervening black holes. — National Geographic, "This Is the Farthest Star Humans Have Ever Seen," 3 Apr. 2018 Both of these results are in line with Dr Yang’s and Dr Urminsky’s hypothesis. — The Economist, "A paradox at the heart of gift-giving," 28 June 2018 The theory is that wilder nature will have more powerful effects, and the researchers offer a few possible reasons for this hypothesis. — Alex Hutchinson, Outside Online, "Why "Wilder" Nature Is Better for Your Health," 27 June 2018 Some companies have stuck with the amyloid hypothesis but have tested such drugs in earlier stages of the disease, on the belief that the older failed trials had patients whose disease was too advanced to be helped. — Peter Loftus, WSJ, "Eli Lilly, AstraZeneca Drop Two Late-Stage Alzheimer’s Drug Trials," 12 June 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.