A more thorough explanation:

Definition: Alba firma (al-bə fər-mə). [Law Latin] See WHITE RENT.

White Rent: A feudal rent paid in silver, rather than in work, grain, or money baser than silver.

Example: In medieval times, a lord might require his tenants to pay a white rent of 10 silver coins per year in exchange for the use of his land.

Explanation: This example illustrates the definition of alba firma because it shows how white rent was a type of feudal payment made in silver, which was considered a valuable and pure form of currency.

Compare: Black rent was another type of feudal payment, but it was paid in a form of currency that was considered less valuable than silver, such as grain or livestock.