pirana vs characin

pirana and characin both are nouns.

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

As nouns, characin is a hypernym of pirana; that is, characin is a word with a broader meaning than pirana:

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

Other hypernyms of pirana include characid, characin fish.

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