In the Roman army during classical antiquity, a centurion (/sɛnˈtjʊəriən/; Latin: centurio [kɛn̪ˈt̪ʊrioː], pl. centuriones; Greek: κεντυρίων, translit. kentyríōn, or Greek: ἑκατόνταρχος, translit. hekatóntarkhos), was a commander, nominally of a century (Latin: centuria), a military unit originally consisting of 100 legionaries. The size of the century changed over time; from the 1st century BC through most of the imperial era it was reduced to 80 men.
A centurion was promoted for being an exemplary soldier and was then expected to become a strict commander of his subordinates, to lead his troops by example, and coordinate his century's actions. They were also responsible for handling logistics and supplies, as well as any discipline that was required. In a Roman legion, centuries were grouped into cohorts and commanded by a senior centurion. The prestigious first cohort (a formation of five double-strength centuries of 160 men each)[1] was led by the primus pilus, who commanded the primi ordines who were the centurions of the first cohort.
A centurion's symbol of office was the vine staff, with which they disciplined even Roman citizens, who were otherwise legally protected from corporal punishment by the Porcian laws.[2] Centurions also served in the Roman navy. They were professional officers, analogous to modern non-commissioned officers in terms of pay-grade, prestige, and responsibilities. In late antiquity and the Middle Ages, the Byzantine army's centurions were known by the name kentarch (Kentarches).[3]