elements could be followed by additional surnames, or cognomina, which could be either personal or hereditary, or a combination of both. The Roman grammarians came to regard the combination of praenomen, nomen, and cognomen as a defining characteristic of Roman citizenship, known as the tria nomina. However, although all three elements of the Roman name existed throughout most of Roman history, the concept of the tria nomina can be misleading, because not all of these names were required or used throughout the whole of Roman history. During the period of the Roman Republic, the praenomen and nomen represented the essential elements of the name; the cognomen first appeared among the Roman aristocracy at the inception of the Republic, but was not widely used among the plebeians, who made up the majority of the Roman people, until the second century BC. Even then, not all Roman citizens bore cognomina, and until the end of the Republic the cognomen was regarded as somewhat less than an official name. By contrast, in imperial times the cognomen became the principal distinguishing element of the Roman name, and although praenomina never completely vanished, the essential elements of the Roman name from the second century onward were the nomen and cognomen. Naming conventions for women also varied from the classical concept of the tria nomina. Originally Roman women shared the binomial nomenclature of men; but over time the praenomen became less useful as a distinguishing element, and women's praenomina were gradually discarded, or replaced by informal names. By the end of the Republic, the majority of Roman women either did not have or did not use praenomina. Most women were called by their nomen alone, or by a combination of nomen and cognomen. Praenomina could still be given when necessary, and as with men's praenomina the practice survived well into imperial times, but the proliferation of personal cognomina eventually rendered women's praenomina obsolete. In the later empire, members of the Roman aristocracy used several different schemes of assuming and inheriting nomina and cognomina, both to signify their rank, and to indicate their family and social connections. Some Romans came to be known by alternative names, or signia, and due to the lack of surviving epigraphic evidence, the full nomenclature of most Romans, even among the aristocracy, is seldom recorded. Thus, although the three types of names referred to as the tria nomina existed throughout Roman history,