Basileus

Basileus (Greek: βασιλεύς) is a Greek term and title that has signified various types of monarchs in history. In the English-speaking world it is perhaps most widely understood to mean "king" or "emperor". The title was used by the Byzantine emperors, and has a longer history of use by sovereigns and other persons of authority in ancient Greece, as well as for the kings of modern Greece.

The feminine forms are basilissa (Βασίλισσα), basileia (Βασίλεια), basilis (Βασιλίς), or the archaic basilinna (Βασιλίννα), meaning "queen" or "empress".

The etymology of basileus is unclear. The Mycenaean form was *gʷasileus (Linear B: ...
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