In ancient Rome, a gens ( or , ; : gentes ) was a family consisting of individuals who shared the same nomen gentilicium and who claimed descent from a common ancestor. A branch of a gens, sometimes identified by a distinct cognomen, was called a stirps (: stirpes). For example, in the name Marcus Tullius Cicero, Tullius is the nomen gentilicium, which identifies Cicero as a member of the Tullia gens, while the surname Cicero identifies the branch of the gens to which he belonged.
The gens was an important social structure at Rome and throughout Italy during the period of the Roman Republic. Much of individuals' social standing depended on the gens to which they belonged. Certain gentes were classified as patrician, others as plebeian; some had both patrician and plebeian branches. The importance of the gens as a social structure declined considerably in imperial times, although the gentilicium continued to define the origins and dynasties of the ancient Romans, including the emperors.
Origins
The word gens is sometimes translated as "race", or "nation", meaning a people descended from a common ancestor. It can also be translated as "clan", "kin", or "tribe", although the word tribus has a separate and distinct meaning in Roman culture. A gens could be as small as a single family, or could include hundreds of individuals. According to tradition, in 479 BC the Fabia gens alone were able to field a militia consisting of three hundred and six men of fighting age. The concept of the gens was not uniquely Roman, but was shared with communities throughout Italy, including those who spoke Italic languages such as Latin, Oscan, and Umbrian as well as the Etruscans, whose language was unrelated. All of these peoples were eventually absorbed into the sphere of Roman culture.
The oldest gentes were said to have originated before the founding of Rome, which most Greek and Roman writers placed in the mid-eighth century BC, and some claimed descent from mythological personages as far back as the time of the Trojan War. However, the establishment of the gens cannot long predate the adoption of hereditary surnames. The nomen gentilicium, or "gentile name", was its distinguishing feature, for a Roman citizen's nomen indicated his membership in a gens. Because some of these things were fairly common, it was possible for unrelated families to bear the same nomen, and over time to become confused. Roman women received their fathers' nomina in their feminine form; Cicero's daughter was named Tullia. They might use additional names when necessary to distinguish them from other women belonging to the same gens. In imperial times, surnames came to serve this function for both men and women.
Praenomina within gentes
In the time of the Republic, it was customary for each son in a family to receive a different praenomen that could be used to distinguish him from his brothers.
Certain families also deliberately avoided particular praenomina. In at least some cases, this was because of traditions concerning disgraced or dishonoured members of the gens bearing a particular name. For example, the Junia gens avoided the praenomina Titus and Tiberius after two members with these names were executed for treason. Similar instances supposedly led the assembly of the Manlia gens to forbid its members from bearing the praenomen Marcus, and caused the Claudii to avoid Lucius. However, these prohibitions were largely traditional, and not strictly enforced, since individuals with most of these names are found at various times.
Cognomina and stirpes
Because there were relatively few praenomina in widespread use, and the same praenomina tended to be used repeatedly within each gens, cognomina were also used to distinguish between individuals and branches of a gens at an early time.
Social function
Members of individual gentes carried out their own religious rites, and some cults were traditionally associated with specific gentes. Reportedly gentiles were responsible for the adoption and guardianship of other members. If a member of a gens died intestate and without immediate family, his property was distributed to the rest of the gens. Roman writers and early modern scholars believed that a gens could establish its own private laws, which were theoretically binding on all of its members. However, no public enactment is recorded as having been passed by the assembly of a gens, and besides sharing common traditions, no means by which a gens could be led or governed is mentioned in any Roman source. Thus, as a group, the gentes had considerable influence on the development of Roman law and religious practices, but comparatively little influence on the political and constitutional history of Rome. According to tradition, the patricians were descended from the "city fathers", or patres; that is, the heads of the family at the time of its foundation by Romulus, the first King of Rome.
Many gentes included both patrician and plebeian branches. These may have arisen through adoption or manumission, or when two unrelated families bearing the same nomen became confused. It may also be that individual members of a gens voluntarily left or were expelled from the patriciate, along with their descendants. In some cases, gentes that must originally have been patrician, or which were so regarded during the early Republic, were later known only by their plebeian descendants.