theory

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 theory about 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

• “the architect has a theory that more is less”
• “they killed him on the theory that dead men tell no tales”