/thee"euh ree, thear"ee/, n., pl. theories.1. a coherent group of general propositions used as principles of explanation for a class of phenomena: Einstein's theory of relativity.2. a proposed explanation whose status is still conjectural, in contrast to well-established propositions that are regarded as reporting matters of actual fact.3. Math. a body of principles, theorems, or the like, belonging to one subject: number theory.4. the branch of a science or art that deals with its principles or methods, as distinguished from its practice: music theory.5. a particular conception or view of something to be done or of the method of doing it; a system of rules or principles.6. contemplation or speculation.7. guess or conjecture.[1590-1600; < LL theoria < Gk theoría a viewing, contemplating, equiv. to theor(eîn) to view + -ia -Y3]Syn. 1. THEORY, HYPOTHESIS are used in non-technical contexts to mean an untested idea or opinion. A THEORY in technical use is a more or less verified or established explanation accounting for known facts or phenomena: the theory of relativity. A HYPOTHESIS is a conjecture put forth as a possible explanation of phenomena or relations, which serves as a basis of argument or experimentation to reach the truth: This idea is only a hypothesis.
* * *(as used in expressions)value theoryacid base theorydouble aspect theorydual aspect theorygerm plasm theorymoney quantity theory oftypes theory of
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