Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
prorate (v.)
meaning “to divide, assess, or share proportionally among those eligible,” is Standard English, an Americanism based on the Latin pro rata, meaning “according to the proportional share.” Pronounce prorate either pro-RAIT or PRO-rait; pronounce pro rata either pro-RA-tuh or pro-RAI-tuh, but use it sparingly except when the jargon of finance, taxes, and other numerical work is appropriate.
