Short answer
A scientific hypothesis is a tentative, testable proposal; a scientific theory is a broader explanation supported by substantial evidence. Both can make predictions, so prediction alone does not distinguish them. In scientific usage, a theory is not merely a guess. 2
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At a glance
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| Attribute | Scientific hypothesis | Scientific theory |
|---|---|---|
| Main role | Propose an explanation or prediction to test | Explain an aspect of nature comprehensively |
| Evidence status | Tentative; open to change | Well substantiated by accumulated evidence |
| Predictive ability | Offers a testable expectation | Predicts unobserved phenomena |
| Everyday-language trap | Treating any guess as scientific | Treating theory as mere speculation |
These contrasts follow LibreTexts’ technical definitions. 2
What each thing is
A hypothesis gives investigation a proposed answer: an explanation of an observation or an expected experimental outcome. A theory supplies an established explanatory account, supported by facts gathered over time. The distinction concerns the explanation’s scientific standing, not simply whether someone has an idea. 2
Key differences
The strongest differences are evidential support and explanatory scope. A hypothesis remains tentative; a theory draws together a body of repeatedly confirmed evidence. The sources do not specify a numerical threshold of experiments or observations that turns one into the other. 2
How to tell them apart
Ask whether the statement presents a proposal awaiting investigation or an explanation supported across a substantial body of evidence. That is a useful identification rule, not a label detector: a prediction can come from either a hypothesis or a theory, so an if–then statement alone is inconclusive. 2
Where they overlap
Both connect ideas with observations and predictions. NASA describes explanatory ideas that account for observed behavior and anticipate what happens next. Hypotheses and theories therefore share scientific work; they are not separated into one category that predicts and another that only explains. 1
Edge cases
An explanation can be called a theory before practical testing becomes possible: NASA notes that scientists could test Einstein’s theories only later. This complicates a rigid naming rule. The same source also describes improvements to heliocentrism, showing that the theory label does not mean an explanation is beyond revision. 1
Why the distinction exists
The terminology separates a proposed answer from an explanation with an established evidential foundation. That separation matters because everyday theory can mean a hunch, whereas scientific theory communicates substantial support. Collapsing those meanings obscures the difference between proposing an explanation and substantiating it. 2
Common misconceptions
A successful prediction should not be treated as an automatic promotion certificate: NASA offers a simplified progression, while LibreTexts emphasizes comprehensive, accumulated support. Nor is theory a halfway point on a ladder to law; LibreTexts distinguishes explanatory theories from laws summarizing patterns. 1 2
Examples
Hypothetical case: a researcher proposes that germs explain a particular illness and specifies a test with an expected result. That proposal functions as a hypothesis; it is distinct from germ theory’s supported explanation that germs cause many diseases. 2
Historical case: NASA’s heliocentrism example explains wandering planetary paths and predicts later positions, illustrating explanatory and predictive work together. 1