Princeps (plural: principes) is a Latin word meaning "first in time or order; the first, foremost,[1] chief, the most eminent, distinguished, or noble; the first person".[2] As a title, princeps originated in the Roman Republic wherein the leading member of the Senate was designated princeps senatus.[3] It is primarily associated with the Roman emperors as an unofficial title first adopted by Augustus (r. 27 BC – AD 14) in 23 BC. Its use in this context continued until the regime of Diocletian (r. 284 – 305 AD) at the end of the third century. He preferred the title of dominus, meaning "lord" or "master".[citation needed] As a result, the Roman Empire from Augustus to Diocletian is termed the "principate" (principatus). Other historians define the reign of Augustus to Severus Alexander (r. 222 – 235) as the Principate, and the period afterwards as the "Autocracy".[4]
The medieval title "Prince" is a derivative of princeps, as is the title Principal.[3]