pentazocine vs painkiller

pentazocine and painkiller both are nouns.

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

As nouns, painkiller is a hypernym of pentazocine; that is, painkiller is a word with a broader meaning than pentazocine:

pentazocine: analgesic drug (trade name Talwin) that is less addictive than morphine
painkiller: a medicine used to relieve pain

Other hypernyms of pentazocine include analgesic, anodyne, pain pill.

pentazocine (noun)	painkiller (noun)
analgesic drug (trade name Talwin) that is less addictive than morphine	a medicine used to relieve pain