cantus firmus

US: (kan′təs fûr′məs)

WordReference Random House Unabridged Dictionary of American English © 2026

can•tus fir•mus  (kan′təs fûr′məs), 

1. Music and Dance the ancient traditional unisonal plainchant of the Christian Church, having its form set and its use prescribed by ecclesiastical tradition.
2. Music and Dance a fixed melody to which other voices are added, typically in polyphonic treatment.

• Medieval Latin: literally, firm song
• 1840–50

Collins Concise English Dictionary © HarperCollins Publishers::

canto fermo / ˈkæntəʊ ˈfɜːməʊ/, cantus firmus / ˈkæntəs ˈfɜːməs/ noun

1. a melody that is the basis to which other parts are added in polyphonic music
2. the traditional plainchant as prescribed by use and regulation in the Christian Church

Etymology: Italian, from Medieval Latin, literally: fixed song