List of Roman army unit types

• Accensus - light legionary soldier.
• Aquilifer - carried the legionary eagle.
• Alaris - a cavalryman
• Armicustos - a soldier tasked with the administration and supply of weapons and equipment. A quartermaster.
• Centurion - officer rank, generally one per century, in charge of century.
• Doctor - a trainer, subdivisions for everything from weapons to hornblowing
• Draconarius - Roman cavalry standard bearer
• Decurion - leads a troop of cavalry (14-30 men). Often confused with decanus.
• Decanus - leads a contubernium (a legionary tent group of 8 men)
• Discens - Miles in training for an immunis position.
• Dux - a general in charge of a legion
• Hastiliarius - a weapons instructor.
• Immunes - those soldiers of the military of ancient Rome who were "immune" from combat duty and fatigues through having a more specialist role within the army
• Legatus - general in the Roman army; literally the "deputy" of the emperor, who was the titular commander-in-chief
• Tiro - The basic private level foot soldier
• Optio - One per century as second-in-command to the centurion. Could also fill several other specialized roles on an ad hoc basis.
• Pilus Prior - The commander of the first century of each cohort.
• Pilus Posterior - Deputy to the pilus prior
• Praefectus Castrorum - camp prefect, third-in-command of the legion, also responsible for maintaining the camp, equipment and supplies. Usually a former primus pilus.
• Praetorians - a special force of bodyguards used by Roman Emperors
• Primus Pilus - (literally 'first file', not spear) the commanding centurion of the first cohort and the senior centurion of the entire Legion
• Protectores Augusti Nostri (aka Protectores Divini Lateris) honorific title for senior officers singled out for their loyalty to the Emperor and soldierly qualities. Constitute an Order of Honour rather than a military unit. First appears in mid-Third Century AD
• Sagittarii - archers, including horse-riding auxiliary archers
• Salararius - a soldier enjoying special service conditions or hired as a mercenary.
• Signifer - Standard bearer of the Roman Legion
• Tablifer - A guard cavalry standard-bearer
• Tesserarius - guard commander, one per century
• Tribuni militum angusticlavii or military tribune -
• Tribunus militum laticlavius - military tribune of senatorial rank. Second in command of a legion.
• Vexillarius - a standard-bearer (carried the Vexillum)

Sub-Units of the Roman legion

In the Pre-Marian reforms the structure of the legions was as follows:

• Turma - a unit of cavalry in the Pre-Marian army, which usually consisted of 30 horsemen

• The cohortes urbanae (urban cohorts) were a body of troops garrisoned at Rome, which was created by Augustus to provide additional security for the emperor and city in general.

• The lictor's main task was to attend as bodyguards to magistrates who held imperium. They carried rods decorated with fasces and, outside the pomerium, with axes that symbolized the power to carry out capital punishment. Dictatorial lictors had axes even within the pomerium.
• Vigiles focused on fighting fires.