The Latin word imperator was originally a title roughly equivalent to commander under the Roman Republic. Later it became a part of the titulature of the Roman Emperors as part of their cognomen. The English word emperor derives from imperator via Old French Empereür. The Roman emperors themselves generally based their authority on multiple titles and positions, rather than preferring any single title. Nevertheless, imperator was used relatively consistently as an element of a Roman ruler's title throughout the principate (derived from princeps, from which prince in English is derived) and the dominate.