Definitions for "Optio"
Low-Level Officers, second in command after the Centurion.
A staff officer who assists the commanding officer.
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 a non-commissioned 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.