The word "monarch" () comes from the Greek language word μονάρχης, monárkhēs (from μόνος monos, "one, singular", and ἄρχω árkhō, "to rule" (compare ἄρχων arkhon, "leader, ruler, chief")) which referred to a single, at least nominally absolute ruler.
Depending on the title held by the monarch, a monarchy may be known as a kingdom, principality, duchy, grand duchy, empire, tsardom, emirate, sultanate, khaganate, etc.