here is a definition for you from <a href="http://www.fsteiger.com/theory.html.QuoteAs">http://www.fsteiger.com/theory.html.QuoteAs</a> used in science, 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.