ED vs impotency

ED and impotency both are nouns.

Word	Noun	Adjective	Verb	Adverb
ED	Yes	No	No	No
impotency	Yes	No	No	No

As nouns, impotency is a hypernym of ED; that is, impotency is a word with a broader meaning than ED:

ED: impotence resulting from a man's inability to have or maintain an erection of his penis
impotency: an inability (usually of the male animal) to copulate

Other hypernyms of ED include impotence, disfunction, dysfunction.

ED (noun)	impotency (noun)
impotence resulting from a man's inability to have or maintain an erection of his penis	the quality of lacking strength or power; being weak and feeble
	an inability (usually of the male animal) to copulate