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Citation

Allan J (2013) Theory. In: Gellman MD & Turner JR (eds.) Encyclopedia of Behavioral Medicine. 1 ed. New York: Springer. https://doi.org/10.1007/978-1-4419-1005-9_1182

Abstract
First paragraph: A theory is a coherent set of statements or ideas used to organize, generalize, explain, and predict phenomena. Theories are based on observations, experimentation, and abstract reasoning, and play a fundamental role in scientific research.