scientific theory

[sahy-uhn-tif-ik theer-ee, thee-uh-ree]

noun

1. a coherent group of propositions formulated to explain a group of facts or phenomena in the natural world and repeatedly confirmed through experiment or observation.

   the scientific theory of evolution.

Word History and Origins

Origin of scientific theory¹

First recorded in 1755–65

When To Use

What is a scientific theory?

A scientific theory is a well-tested, broad explanation of a natural phenomenon.In everyday life, we often use the word theory to mean a hypothesis or educated guess, but a theory in the context of science is not simply a guess—it is an explanation based on extensive and repeated experimentation. And it’s not the job of theories to become facts—they use available facts to make sense of a broad concept.Scientific theories explain some of the most familiar and complex phenomena. A few of the best-known scientific theories are the theory of gravity, the theory of evolution, and the theory of relativity.