Definition of per mensem in English:
per mensem
adverb
Chiefly with reference to a sum of money: (so much) every month, for or in each month, monthly.
Origin
Early 17th century. From classical Latin per mēnsem in the course of a month, for the space of a month from per + mēnsem, accusative of mēnsis month.
Pronunciation
per mensem
/pəː ˈmɛnsɛm/