The precarium (plural precaria)—or precaria (plural precariae) in the feminine form—is a form of land tenure in which a petitioner (grantee) receives a property for a specific amount of time without any change of ownership. The precarium is thus a free gift made on request (or precarius, whence "prayer") and can be revoked. The grantor can reclaim the land and evict the grantee at any time, and the grantee's hold on the land is said to be "precarious". (The adjectival form "precarial" is also used.) The precarium arose in the late Roman Empire. In the Middle Ages it became a legal fiction, and the two parties usually signed a contract specifying the rent or services owed by the petitioner. Some precaria eventually became hereditary fiefs. In the Merovingian period the feminine form (singular precaria) became common, but in the eighth century the term beneficium began to replace precarium, although the institutions were practically identical.