live-bearer vs molly

live-bearer and molly both are nouns.

Word	Noun	Adjective	Verb	Adverb
live-bearer	Yes	No	No	No
molly	Yes	No	No	No

As nouns, molly is a hyponym of live-bearer; that is, molly is a word with a more specific, narrower meaning than live-bearer:

live-bearer: small usually brightly-colored viviparous surface-feeding fishes of fresh or brackish warm waters; often used in mosquito control
molly: popular aquarium fish

Other hyponyms of live-bearer include Gambusia affinis, mosquitofish, platy, Platypoecilus maculatus, mollie.

live-bearer (noun)	molly (noun)
small usually brightly-colored viviparous surface-feeding fishes of fresh or brackish warm waters; often used in mosquito control	popular aquarium fish