 Together, these were referred to as the "tria nomina".Although not all Romans possessed three names, the practice of using multiple names having different functions was a defining characteristic of Roman culture that distinguished citizens from foreigners.The praenomen was a true personal name, chosen by a child's parents, and bestowed on the "dies lustricius", or "day of lustration", a ritual purification performed on the eighth day after the birth of a girl, or the ninth day after the birth of a boy.