Meaning & Definition of Theory in English

1. 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"

2. 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"

3. 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"