characin vs pirana

characin and pirana both are nouns.

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

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

characin: 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 include tetra, cardinal tetra, Paracheirodon axelrodi, caribe, piranha.

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