Dominus (title)

Roman imperial use

Originating from its use by slaves to address their masters, the title was sporadically used in addressing emperors throughout the Principate, usually in the form of excessive flattery (or political invective) when referring to the emperor. As a title of sovereignty, the term under the Roman Republic had all the associations of the Greek Tyrannos; refused during the early Principate, it finally became an official title of the Roman Emperors under Diocletian. Augustus actively discouraged the practice, and Tiberius in particular is said to have reviled it as sycophancy. Domitian encouraged its use, but none of the emperors used the term in any semi-official capacity until the reign of Aurelian in AD 274, where coins were issued bearing the inscription deus et dominus natus.

However, under Diocletian the term dominus was adopted as part of the emperor's official titulature, forming part of Diocletian's radical reforms. It's from this use that the term Dominate is sometimes used to refer to the period of Roman history beginning with the reign of Diocletian.

English use

The feminine form Domina was a title formerly given to noble ladies who held a barony in their own right in old English Law. Many female honorifics used in modern English trace their roots back to this title, through the Anglo-French and still extant in modern French, dame and madame. The most common are madam and its contracted form ma'am. Another notable example is Dame, a more narrow equivalent to Sir used for recipients of chivalric honors. (Damehood being the equivalent to the male knighthood.)

Cambridge University continues to use both Dominus and Domina, abbreviated as Dnus. and Dna. respectively, for those who have achieved a BA, and its derived term Don continues to see use in reference to professors, lecturers, and fellows at Oxford and Cambridge.