definition of
theory

[1] #1 theory n. 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 hypothes. wn

[2] #2 theory n. [hypothesis, possibility] 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. wn

[3] #3 theory n. 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". wn