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theory - definition and synonyms


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noun theory pronunciation in British English /ˈθɪəri/
Word Forms
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  1. 1
    [countable] one or more ideas that explain how or why something happens
    The theory predicts low speeds and therefore safety.
    theory that: He had a theory that the germs caused disease.
  2. 2
    [uncountable] the set of general principles that a particular subject is based on
    the theory and practice of education
    psychoanalytic/Marxist/literary theory
  3. 3
    [countable] an idea that you believe is true although you have no proof
    theory about: I have my own theory about why he resigned.
    theory that: There is a theory that her death was an accident.


a course of study which is much shorter than a university course and focuses on the skills you need for a job, especially computer-related skills

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an ancient Roman system of underfloor heating, used to heat houses with hot air; from the Latin 'hypocaustum'

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