characid vs tetra

characid and tetra both are nouns.

Word	Noun	Adjective	Verb	Adverb
characid	Yes	No	No	No
tetra	Yes	No	No	No

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

Other hyponyms of characid include cardinal tetra, Paracheirodon axelrodi, caribe, pirana, piranha.

characid (noun)	tetra (noun)
any freshwater fish of the family Characinidae	brightly colored tropical freshwater fishes