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; theories can incorporate facts and laws and tested hypotheses; true in fact and theory'

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

[ Syn: hypothesis , possibility ]

a belief that can guide behavior; the architect has a theory that more is less; they killed him on the theory that dead men tell no tales'