Definition of theory noun from the Oxford Advanced American Dictionary

        

    theory

     noun
    noun
    NAmE//ˈθɪri//
     
    , NAmE//ˈθiəri//
     
    (pl. theories)
     
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  1. 1 [countable, uncountable] a formal set of ideas that is intended to explain why something happens or exists According to the theory of relativity, nothing can travel faster than light. The debate is centered around two conflicting theories. Topic CollocationsScientific Researchtheory formulate/advance a theory/hypothesis build/construct/create/develop a simple/theoretical/mathematical model develop/establish/provide/use a theoretical/conceptual framework/an algorithm advance/argue/develop the thesis that… explore an idea/a concept/a hypothesis make a prediction/an inference base a prediction/your calculations on something investigate/evaluate/accept/challenge/reject a theory/hypothesis/modelexperiment design an experiment/a questionnaire/a study/a test do research/an experiment/an analysis make observations/calculations take/record measurements carry out/conduct/perform an experiment/a test/a longitudinal study/observations/clinical trials run an experiment/a simulation/clinical trials repeat an experiment/a test/an analysis replicate a study/the results/the findings observe/study/examine/investigate/assess a pattern/a process/a behavior fund/support the research/project/study seek/provide/get/secure funding for researchresults collect/gather/extract data/information yield data/evidence/similar findings/the same results analyze/examine the data/soil samples/a specimen consider/compare/interpret the results/findings fit the data/model confirm/support/verify a prediction/a hypothesis/the results/the findings prove a conjecture/hypothesis/theorem draw/make/reach the same conclusions read/review the records/literature describe/report an experiment/a study present/publish/summarize the results/findings present/publish/read/review/cite a paper in a scientific journal
  2. 2[uncountable] the principles on which a particular subject is based the theory and practice of language teaching literary theory
  3. 3[countable] theory (that…) an opinion or idea that someone believes is true but that is not proved I have this theory that most people prefer being at work to being at home.
  4. AWL Collocationstheorytheory noundevelop, formulate advance, expound, propound disprove, refute support testIn this study, the empirical data do not support current theories. New facts and observations test established theories.hypothesize, posit, postulate, predict, suggestThe theory posits that some character types are better prepared for the challenges of being president. The results of our experiment aligned very closely with that predicted by theory.economic, literary, political, scientific, socialIn economic theory, when there is more competition prices are lower.based onBased on the theory developed in this paper, it is predicted that..theoretical adjectivehighly largely merely, purelyAlthough some purely theoretical work has been done, there is a need for empirical research.concept, construct, framework, model approach, perspective prediction studyThe next section outlines the theoretical framework and reviews the prior literature.theoretically adverbdefensible, informed, sound unsoundThese scientific hypotheses have to be logically and theoretically defensible.Idioms used to say that a particular statement is supposed to be true but may in fact be wrong In theory, these machines should last for ten years or more. That sounds fine in theory, but have you really thought it through? “Aren't you supposed to be retired?” “Yes, in theory.”
See the Oxford Advanced Learner's Dictionary entry: theory