diabolus

Diabolus is the Latin term for the devil, used in Christian theological, liturgical, and literary contexts. The word derives from Greek diabolos, via Latin diabolus, and is connected to the idea of an accuser or slanderer. In medieval and early modern Europe, diabolus was employed as a general reference to the Devil or demonic beings in religious writings, sermons, and translations.

In music, the phrase diabolus in musica, meaning “the devil in music,” refers to the tritone, an interval spanning three whole tones (an augmented fourth or diminished fifth). The tritone was perceived as highly dissonant in medieval and Renaissance theory and was often described as dangerous or forbidden, sometimes associated with evil or the devil. Over time, composers and theorists moved away from such strict avoidance, and the tritone became a fundamental component of tonal harmony in later Western music.

Beyond religious and musical contexts, diabolus appears in demonology and literature as a personification or epithet for the devil. In modern usage, the term may surface in fantasy fiction, occult writings, or historical discussions of Latin-language religious texts. The best-known contemporary association remains the musical “diabolus in musica,” illustrating the longstanding cultural link between the figure of the devil and dissonant sound.