hydromorphone vs pain pill

hydromorphone and pain pill both are nouns.

Word	Noun	Adjective	Verb	Adverb
hydromorphone	Yes	No	No	No
pain pill	Yes	No	No	No

As nouns, pain pill is a hypernym of hydromorphone; that is, pain pill is a word with a broader meaning than hydromorphone:

hydromorphone: a narcotic analgesic (trade name Dilaudid) used to treat moderate to severe pain
pain pill: a medicine used to relieve pain

Other hypernyms of hydromorphone include analgesic, anodyne, painkiller.

hydromorphone (noun)	pain pill (noun)
a narcotic analgesic (trade name Dilaudid) used to treat moderate to severe pain	a medicine used to relieve pain