A tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena


A scientific hypothesis that survives experimental testing becomes a scientific theory

He proposed a fresh theory of alkalis that later was accepted in chemical practices

A belief that can guide behavior

Type of



The architect has a theory that more is less

They killed him on the theory that dead men tell no tales

A well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena