imperium vs potency

imperium and potency both are nouns.

Word	Noun	Adjective	Verb	Adverb
imperium	Yes	No	No	No
potency	Yes	No	No	No

As nouns, potency is a hypernym of imperium; that is, potency is a word with a broader meaning than imperium:

Other hypernyms of imperium include authorisation, authority, authorization, dominance, say-so.

imperium (noun)	potency (noun)
supreme authority; absolute dominion	capacity to produce strong physiological or chemical effects
the domain ruled by an emperor or empress; the region over which imperial dominion is exercised	the power or right to give orders or make decisions
	the state of being potent; a male's capacity to have sexual intercourse
	the inherent capacity for coming into being