Roman candle vs firework

Roman candle and firework both are nouns.

Word	Noun	Adjective	Verb	Adverb
Roman candle	Yes	No	No	No
firework	Yes	No	No	No

As nouns, firework is a hypernym of Roman candle; that is, firework is a word with a broader meaning than Roman candle:

Roman candle: a cylindrical firework that projects a series of colored balls of fire
firework: (usually plural) a device with an explosive that burns at a low rate and with colored flames; can be used to illuminate areas or send signals etc.

Other hypernyms of Roman candle include pyrotechnic.

Roman candle (noun)	firework (noun)
a cylindrical firework that projects a series of colored balls of fire	(usually plural) a device with an explosive that burns at a low rate and with colored flames; can be used to illuminate areas or send signals etc.