The Roman household was conceived of as an economic and juridical unit or estate: "familia" originally meant the group of the "famuli" (the "servi" or serfs and the slaves of a rural estate) living under the same roof. That meaning later expanded to indicate the "familia" as the basic Roman social unit, which might include the "domus" (house or home) but was legally distinct from it: a "familia" might own one or several homes. All members and properties of a "familia" were subject to the authority of a "pater familias": his legal, social and religious position defined "familia" as a microcosm of the Roman state. In Roman law, the "potestas" of the "pater familias" was official but distinct from that of magistrates.