A scientific theory summarizes a hypothesis or group of hypotheses that have been supported with repeated testing.
If enough evidence accumulates to support a hypothesis, it moves to the next step and is called a theory. In the scientific method, a theory is considered to be a valid explanation of a phenomenon.
When used in non-scientific context, the word “theory” implies that something is unproven or speculative. As used in science, however, a theory is an explanation or model based on observation, experimentation, and reasoning, especially one that has been tested and confirmed as a general principle helping to explain and predict natural phenomena.
Any scientific theory must be based on a careful and rational examination of the facts. In the scientific method, there is a clear distinction between facts, which can be observed and/or measured, and theories, which are scientists’ explanations and interpretations of the facts. Scientists can have various interpretations of the outcomes of experiments and observations, but the facts, which are the cornerstone of the scientific method, do not change.