governor vs proconsul

governor and proconsul both are nouns.

Word	Noun	Adjective	Verb	Adverb
governor	Yes	No	No	No
proconsul	Yes	No	No	No

As nouns, proconsul is a hyponym of governor; that is, proconsul is a word with a more specific, narrower meaning than governor:

governor: the head of a state government
proconsul: a provincial governor of consular rank in the Roman Republic and Roman Empire

Other hyponyms of governor include bey, eparch, governor general, military governor, nabob, nawab, satrap, vicereine, viceroy.

governor (noun)	proconsul (noun)
a control that maintains a steady speed in a machine (as by controlling the supply of fuel)	an anthropoid ape of the genus Proconsul
the head of a state government	a provincial governor of consular rank in the Roman Republic and Roman Empire
	an official in a modern colony who has considerable administrative power