This paper aims to provide an overview of the concept of colloquial language (“sermo familiaris”) as defined by scholars from different periods, both in the Modern Age and the Contemporary Age. It then establishes the theoretical basis from which one can analyse colloquial expressions, which is why it refers, on the one hand, to rhetoric as the discipline from which colloquialisms are studied and, on the other, to the link between grammar and rhetoric (“elocutio”). With regard to this alliance between stylistics and grammar, the contributions of various modern and contemporary scholars are noteworthy. The article then illustrates the uses of colloquial language with quotations from Horace’s Epodes. The criteria for classifying colloquialisms come from Hofmann’s contributions within the affective phrase constructed exclusively or predominantly with affective exponents. Hofmann’s definition connects with Aristotle’s Art of Poetry (Arist. Po. 1456b. 2-7); the Stagirite establishes the interrelationship between language and thought with its different manifestations of feelings. In line with the two previous scholars, Christoforo Landino (1424-1498), Denis Lambin (1520-1572) and Richard Bentley (1662-1742) address colloquialisms found in Horace’s Epodes in their annotations.