ˈthēərē, ˈthi(ə)r-, -ri sometimes ˈthēr- noun
( -es )
Etymology: Late Latin theoria, from Greek theōria act of viewing, contemplation, consideration, theory, from theōrein to look at, behold, contemplate, consider + -ia -y — more at theorem
1. archaic : imaginative contemplation of reality : direct intellectual apprehension : insight
nor can I think I have the true theory of death when I contemplate a skull — Sir Thomas Browne
2.
a. : a belief, policy, or procedure proposed or followed as the basis of action : a principle or plan of action
educational system, based on the theory that men learn better from actual experience than from books — American Guide Series: Michigan
wanted to kill him, presumably on the theory that dead men tell no tales — D.D.Martin
the hedonistic theory of ethics
b. : an ideal or hypothetical set of facts, principles, or circumstances
the days when law and order was more of a theory than a fact — Seth Agnew
— often used in the phrase in theory
the failure in practice of what looked so promising in theory
3.
a.
(1) : the body of generalizations and principles developed in association with practice in a field of activity (as medicine, music) and forming its content as an intellectual discipline : pure as distinguished from applied art or science
spent two years … in the study of theory and piano — W.T.Upton
made a distinct contribution to museum theory and practice — R.F.Bach
(2) : the coherent set of hypothetical, conceptual, and pragmatic principles forming the general frame of reference for a field of inquiry (as for deducing principles, formulating hypotheses for testing, undertaking actions)
the importance of theory if research is to be significant and its findings are to be cumulative — Pendleton Herring
anthropological theory
contributions to the theory of knowledge
(3) : a body of mathematical theorems presenting a clear, rounded, and systematic view of a subject
theory of equations
theory of probability
— see theory of numbers
b. : abstract knowledge
necessary … in designing retaining walls to be guided by experience rather than by theory — G.T.Snelling
the period of transition from theory to practice in the study of shorthand — J.R.Gregg
c.
(1) : a field of intellectual inquiry
literary critics badly need the sort of foundation that such … inquiries as theory of signs and theory of value could give them — P.B.Rice
(2) : a systematic analysis, elucidation, or definition of a concept
study the philosophers' conflicting theories of right
— see coherence theory
4. : a judgment, conception, proposition, or formula (as relating to the nature, action, cause, or origin of a phenomenon or group of phenomena) formed by speculation or deduction or by abstraction and generalization from facts
her theory of the relationship of order to disorder in the language of poetry — Archibald MacLeish
the wave theory of light
the theory that the individual recapitulates the development of the race
the gesture theory of the origin of language
the emotive theory of value judgments
as
a. : a hypothetical entity or structure explaining or relating an observed set of facts
the Freudian theory of the superego
the Greek theory of the atom
b. : a working hypothesis given probability by experimental evidence or by factual or conceptual analysis but not conclusively established or accepted as a law
the theory of relativity
the theory that compounds in dilute solutions obey the same laws that apply to gases
the theory of radioactive decay
a theory of exchange rates which is merely a special case of the general theory of exchange and markets — K.E.Boulding
5. : something taken for granted especially on trivial or inadequate grounds : conjecture , speculation , supposition
her theory that the house was once occupied by spies