A centurion (; , . ; , or ) was a position in the Roman army during classical antiquity, nominally the commander of a century (), a military unit originally consisting of 100 legionaries. The size of the century changed over time, and from the first century BC through most of the imperial era was reduced to 80 men. In a Roman legion, centuries were grouped into cohorts and commanded by their senior-most centurion. The prestigious first cohort was led by the primus pilus, the most senior centurion in the legion and its fourth-in-command who was next in line for promotion to Praefectus Castrorum, and 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. Centurions also served in the Roman navy. After the 107 BC Marian reforms of Gaius Marius, centurions were professional officers. In Late Antiquity and the Middle Ages, the Byzantine army's centurions were also known by the name kentarch (Kentarches). Role In the Roman infantry, the centurions commanded a centuria or "century". During the Mid-Republic these centuries were grouped in pairs to make up a maniple, each century consisting of 30–60 men. After the Marian reforms a century typically composed of around 80 men, with six such centuries forming a legionary cohort. Later, generals and emperors further manipulated these numbers with double and half-strength units. Julius Caesar, for instance, made the first cohort of five double strength centuries. Centurions received a much higher rate of pay than the average legionary. Veteran legionaries often worked as tenants of their former centurions. During the Imperial era, centurions gradually rose in seniority in their cohort, commanding centuries with higher precedence, until commanding the senior century and therefore the whole cohort. The best centurions were then promoted to the first cohort and known as the Primi Ordines, commanding one of the cohort's five centuries and also taking on a staff role. The most senior centurion of the legion was the Primus Pilus who commanded the first century of the first cohort. All centurions, however senior, had their own allocated century. There was little difference between the ranks of centurions except for the Primus Pilus, who also participated in war councils. The Primus Pilus was so called because his own century was