can·tus fir·mus 
(kăn′təs fîrməs, fûr-)
(kăn′təs fîrməs, fûr-)n.
A preexisting melody used as the basis of a polyphonic composition, especially in polyphony of the 1300s and 1400s.
[Medieval Latin : Latin cantus, song + Latin firmus, fixed.]
- semihard
- semiheavy water
- semi-independent
- semi-infinite
- semiliquid
- semiliquidity
- semiliteracy
- semiliterate
- Semillon
- semilog
- semilogarithmic
- semilunar
- semilunar bone
- semilunar cartilage
- semilunar valve
- semilunate
- semimembranous
- semimonthly
- seminal
- seminal duct
- seminal fluid
- seminally
- seminal vesicle
- seminar
- seminarian