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".

What is the meaning of Basileus?

: a ruler of the Eastern Roman Empire.

What do you call a Greek king?

Anax (Greek: ἄναξ; from earlier ϝάναξ, wánax) is an ancient Greek word for "tribal chief, lord, (military) leader". It is one of the two Greek titles traditionally translated as "king", the other being basileus, and is inherited from Mycenaean Greece, and is notably used in Homeric Greek, e.g. for Agamemnon.