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.