Firn

се́рен

séren

(A type of old snow which has gone through multiple thaw and refreeze cycles)

се́рень

sérenʹ

(A type of old snow which has gone through multiple thaw and refreeze cycles)

серена́

serená

(A type of old snow which has gone through multiple thaw and refreeze cycles)

серён

serjón

(A type of old snow which has gone through multiple thaw and refreeze cycles)

фирн

firn

(A type of old snow which has gone through multiple thaw and refreeze cycles)