Optio

An Optio (from the Latin verb optare, 'to choose', because an Optio was chosen by his centurion) was a soldier in the Roman army who held a position similar to that of an Executive Officer in modern armies. The main function of an Optio was as an Optio centuriae, the second-in-command of a centuria (century), although there were many other positions an Optio could hold. Optios were vital units in the late Roman army, as casualties were often high among Centurions due to their position at the... full article at wikipedia