theory Meaning, Definition & Usage

  1. noun 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. noun a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena
    hypothesis; possibility.
    • 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. noun 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

WordNet

The"o*ry noun
Etymology
F. théorie, L. theoria, Gr. a beholding, spectacle, contemplation, speculation, fr. a spectator, to see, view. See Theater.
Wordforms
plural Theories
Definitions
  1. A doctrine, or scheme of things, which terminates in speculation or contemplation, without a view to practice; hypothesis; speculation. ✍ "This word is employed by English writers in a very loose and improper sense. It is with them usually convertible into hypothesis, and hypothesis is commonly used as another term for conjecture. The terms theory and theoretical are properly used in opposition to the terms practice and practical. In this sense, they were exclusively employed by the ancients; and in this sense, they are almost exclusively employed by the Continental philosophers." Sir W. Hamilton.
  2. An exposition of the general or abstract principles of any science; as, the theory of music.
  3. The science, as distinguished from the art; as, the theory and practice of medicine.
  4. The philosophical explanation of phenomena, either physical or moral; as, Lavoisier's theory of combustion; Adam Smith's theory of moral sentiments. Syn. -- Hypothesis, speculation. -- Theory, Hypothesis. A theory is a scheme of the relations subsisting between the parts of a systematic whole; an hypothesis is a tentative conjecture respecting a cause of phenomena.

Webster 1913