The Roman army (Latin: , literally: Roman Army; Ancient Greek: , transcription: stratos Romaion) is a term encompassing the terrestrial armed forces deployed by the Roman Kingdom (to c. 500 BC), the Roman Republic (500–31 BC), the Roman Empire (31 BC – 395/476 AD) and its successor the East Roman or Byzantine Empire. It is thus a term that spans approximately 2,000 years, during which the Roman armed forces underwent numerous permutations in composition, organization, equipment and tactics, while conserving a core of lasting traditions.