Princeps

Princeps (plural: principes) is a Latin word meaning "first in time or order; the first, foremost, chief, the most eminent, distinguished, or noble; the first person". As a title, princeps originated in the Roman Republic wherein the leading member of the Senate was designated princeps senatus. 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". 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".

The medieval title "Prince" is a derivative of princeps.