pro rata

Definition from Nolo’s Plain-English Law Dictionary

(proh-rat-ah or proh-ray-tah) From Latin for "in proportion," refers to a share to be received or an amount to be paid based on the fractional share of ownership, responsibility, or time used. For example, a buyer of rental property will pay his or her pro rata share of the property taxes for that portion of the year in which he or she holds title.

Definition provided by Nolo’s Plain-English Law Dictionary.