grassfinch vs weaver finch

grassfinch and weaver finch both are nouns.

Word	Noun	Adjective	Verb	Adverb
grassfinch	Yes	No	No	No
weaver finch	Yes	No	No	No

As nouns, weaver finch is a hypernym of grassfinch; that is, weaver finch is a word with a broader meaning than grassfinch:

grassfinch: usually brightly-colored Australian weaverbirds; often kept as cage birds
weaver finch: finch-like African and Asian colonial birds noted for their elaborately woven nests

Other hypernyms of grassfinch include weaver, weaverbird.

grassfinch (noun)	weaver finch (noun)
usually brightly-colored Australian weaverbirds; often kept as cage birds	finch-like African and Asian colonial birds noted for their elaborately woven nests