theorynounfeminine/teˈoɾiɐ/mediumte·o·ri·aPortuguesEnglishEspanolFrancaisDefinitionA set of principles or ideas that explain a phenomenon.The theory of evolution is widely accepted.He presented a new theory about the origin of the universe.syndoctrineprincipleEtymologyDo grego 'theoria'Related wordsteóricoteorizarteoria da relatividade