|Roman numeral analysis symbols|
|Roman Numeral||Triad quality||Example (tonic)|
|Lowercase o||Diminished triad||io|
|Uppercase +||Augmented triad||I+|
Developed in the 19th century for the purpose of harmonic analysis, "the roman numeral system is limited to classical harmony (closely related diatonic chords and key centers)," and alternatives include the functional hybrid Nashville number system and macro analysis.