painkiller vs morphia

painkiller and morphia both are nouns.

Word	Noun	Adjective	Verb	Adverb
painkiller	Yes	No	No	No
morphia	Yes	No	No	No

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

painkiller: a medicine used to relieve pain
morphia: an alkaloid narcotic drug extracted from opium; a powerful, habit-forming narcotic used to relieve pain

painkiller (noun)	morphia (noun)
a medicine used to relieve pain	an alkaloid narcotic drug extracted from opium; a powerful, habit-forming narcotic used to relieve pain