: gentes [ˈgɛnteːs]) was a family consisting of individuals who shared the same nomen gentilicium and who claimed descent from a common ancestor.
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.
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.
[1][4][5][6] The nomen could be derived from any number of things, such as the name of an ancestor, a person's occupation, physical appearance, character, or town of origin.
A libertus, or "freedman", usually assumed the nomen (and sometimes also the praenomen) of the person who had manumitted him, and a naturalized citizen usually took the name of the patron who granted his citizenship.
Freedmen and newly enfranchised citizens were not technically part of the gentes whose names they shared, but within a few generations it often became impossible to distinguish their descendants from the original members.
[1][4] Most gentes regularly employed a limited number of personal names, or praenomina, the selection of which helped to distinguish members of one gens from another.
A similar instance supposedly led the assembly of the Manlia gens to forbid its members from bearing the praenomen Marcus, although this prohibition does not seem to have been strictly observed.
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.
Other noble families which came to Rome during the time of the kings were also admitted to the patriciate, including several who emigrated from Alba Longa after that city was destroyed by Tullus Hostilius.
Another law promulgated as part of the tables forbade the intermarriage of patricians and plebeians, but this was repealed after only a few years, by the Lex Canuleia in 445 BC.
The emperor Constantine and his successors revived the title as a mark of distinction granted to individuals, rather than a class to which an entire family belonged.