Male names typically contain three proper nouns which are classified as praenomen (or given name), nomen (or Gens name) and cognomen. Sometimes a second cognomen (called agnomen) is added.
For female names, there are a few differences. When applying for citizenship, only the praenomen, nomen, and cognomen are mandatory, while additional elements such as agnomen and filiation are optional.
Praenomen This form of "first" name, except for familiar or friendly use, was relatively unimportant, and was not frequently used on its own. There are only a relative few praenomina that were commonly known in both the Republican and Imperial eras of Rome. Only a couple of the names, such as Marcus (as Mark) and Lucius (and its feminine form Lucia) survived into modern times.
Many of the praenomina used by male citizens were abbreviated to one or two characters in writing or inscriptions; the more common abbreviations include: Appius (Ap.), Flavius (Fl.), Gaius (C.), Gnaeus (Cn.), Lucius (L), Manius (M'), Marcus (M), Publius (P), Servius (Ser.), Sextus (Sex.), Spurius (Sp.), Titus (T), Tiberius (Ti.). The names Secundus, Tertius, Quintus, Sextus, and Decimus mean, respectively, 'second', 'third', 'fifth', 'sixth', and 'tenth', and were typically given to second, third, etc. sons in birth order.
Cognomen The third name, or cognomen, started to be a nickname or personal name that distinguished individuals within the same Gens (the cognomen does not appear in official documents until around 100 BC). During the Roman Republic and Empire, the cognomen is inherited from father to son, serving to distinguish a family within a Gens. Often the cognomen was chosen based on some physical or personality trait.
Hundreds of cognomina are known. See list of Roman cognomina for a comprehensive list.
Agnomen A distinction could even be made in families, a second cognomen (called agnomen) being added. A few of these were inherited like the cognomen, thus establishing a sub-family within a family. Nevertheless, the majority were used as nicknames. Sometimes it served an honorific purpose as the result of an important deed.
Foreign names As Rome continued to conquer territories beyond the Italian peninsula, many foreign names were introduced. Discharged auxiliary soldiers and others gaining Roman Citizenship could, and many would, continue to use at least a portion of their former names. A number of the names below are of Greek origin, while others came from regions that were brought under Roman influence. Non-citizen auxiliary soldiers who were granted citizenship, often adopted the nomen of their Emperor, adding their native name as a cognomen.
Female names There is inscriptional evidence to show that in the earliest period there were female versions of the praenomina and that women's names presumably consisted of a praenomen and nomen followed by filiation. By the time of the historically attested Republic, women no longer normally had praenomina. Instead, they were officially known only by the female form of their father's nomen. If further description was needed, the name was followed by the genitive of her father's nomen or, after marriage, of her husband. Hence, Cicero speaks of a woman as Annia P. Anni senatoris filia (Annia the daughter of P. Annius the senator). If only two daughters survived they could be distinguished as maior and minor. Mark Antony's daughters were known as Antonia maior (grandmother of the emperor Nero) and Antonia minor (mother of the emperor Claudius). More than two daughters were distinguished by ordinal numbers: Cornelia Quinta, the fifth daughter of a Cornelius. By the late Republic, women also adopted the female form of their father's cognomen (e.g., Caecilia Metella Crassi, daughter of Q. Caecilius Metellus and wife of P. Licinius Crassus). This feminized cognomen was often made a diminutive (e.g., Augustus's wife Livia Drusilla was the daughter of a M. Livius Drusus).
ADDITIONAL ELEMENTS AND EXAMPLES In the beginning, the praenomen and nomen constituted a Roman's full name and were followed by the so-called filiation (a patronymic or indication of paternity). The filiation (patronimicus) consisted of the Latin word for "son" filius (abbreviated by the letter f.) preceded by the abbreviation of the father's praenomen, which was understood in the genitive. Hence, a Roman might have been known as M. Antonius M. f. (=Marci filius), that is, Marcus Antonius, the son of Marcus. Additionally it could also indicate the grandfather with the word "grandson" nepos (abbreviated by the letter n.). By the Middle Republic, the abbreviation for tribe in which the man was enrolled was added after his filiation. When this became an official part of the name is not known. By 242 BC the number of tribes was fixed at 35:
A tribe was not an indication of common ancestry; the tribes were distributed geographically and a man belonged to the tribe in which his main residence was located. The tribe was an essential part of citizenship, since voting was often carried out by tribe. With the expansion of the Empire, the number or tribes also expanded.
Analysis of the example of a complete name: Marcus Aurelius Marci f. Quinti n. tribu Galeria Antoninus Pius, domo Caesaraugusta.
In everyday use, people are referred to by either a combination of the praenomen and nomen, or even more usually by just their cognomen. So, "Marcus Livius Drusus" would either be just "Drusus" or "Marcus Livius". "Iulia Marciana" would be just "Iulia".