characin fish vs pirana

characin fish and pirana both are nouns.

Word	Noun	Adjective	Verb	Adverb
characin fish	Yes	No	No	No
pirana	Yes	No	No	No

As nouns, pirana is a hyponym of characin fish; that is, pirana is a word with a more specific, narrower meaning than characin fish:

characin fish: any freshwater fish of the family Characinidae
pirana: small voraciously carnivorous freshwater fishes of South America that attack and destroy living animals

Other hyponyms of characin fish include tetra, cardinal tetra, Paracheirodon axelrodi, caribe, piranha.

characin fish (noun)	pirana (noun)
any freshwater fish of the family Characinidae	small voraciously carnivorous freshwater fishes of South America that attack and destroy living animals