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English definition of “theory”

theory

noun
 
 
/ˈθɪəri/
IDEA [C] B2 an idea or set of ideas that is intended to explain something: Darwin's theory of evolutionPhilosophyIdeas, concepts and theories
PRINCIPLES [U] the set of principles on which a subject is based: economic theoryPhilosophyIdeas, concepts and theories
in theory B2 If something is possible in theory, it should be possible but often it does not happen this way: In theory, the journey should be shorter but in practice, the roadworks slow you down.Ideas, concepts and theories
(Definition of theory from the Cambridge Learners Dictionary © Cambridge University Press)
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