Meaning : 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.
Example :
Theories can incorporate facts and laws and tested hypotheses.
True in fact and theory.
Meaning : A tentative insight into the natural world. A concept that is not yet verified but that if true would explain certain facts or phenomena.
Example :
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.
Synonyms : hypothesis, possibility
Meaning : A belief that can guide behavior.
Example :
The architect has a theory that more is less.
They killed him on the theory that dead men tell no tales.