Hypothesis Definition (Science)

A hypothesis is a proposed prediction or explanation that is tested by an experiment.
A hypothesis is a proposed prediction or explanation that is tested by an experiment. MiguelMalo / Getty Images

A hypothesis is an explanation that is proposed for a phenomenon. Formulating a hypothesis is a step of the scientific method.

Alternate Spellings: plural: hypotheses

Examples: Upon observing that a lake appears blue under a blue sky, you might propose the hypothesis that the lake is blue because it is reflecting the sky. One alternate hypothesis would be that the lake is blue because water is blue.

Hypothesis Versus Theory

Although in common usage the terms hypothesis and theory are used interchangeably, the two words mean something different from each other in science. Like a hypothesis, a theory is testable and may be used to make predictions. However, a theory has been tested using the scientific method many times. Testing a hypothesis may, over time, lead to the formulation of a theory.

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Helmenstine, Anne Marie, Ph.D. "Hypothesis Definition (Science)." ThoughtCo, Dec. 9, 2017, thoughtco.com/definition-of-hypothesis-605234. Helmenstine, Anne Marie, Ph.D. (2017, December 9). Hypothesis Definition (Science). Retrieved from https://www.thoughtco.com/definition-of-hypothesis-605234 Helmenstine, Anne Marie, Ph.D. "Hypothesis Definition (Science)." ThoughtCo. https://www.thoughtco.com/definition-of-hypothesis-605234 (accessed April 22, 2018).