Meaning of THEORY in English

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


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



(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


(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


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

Webster's New International English Dictionary.      Новый международный словарь английского языка Webster.