true frog vs grass frog

true frog and grass frog both are nouns.

Word	Noun	Adjective	Verb	Adverb
true frog	Yes	No	No	No
grass frog	Yes	No	No	No

As nouns, grass frog is a hyponym of true frog; that is, grass frog is a word with a more specific, narrower meaning than true frog:

true frog: insectivorous usually semiaquatic web-footed amphibian with smooth moist skin and long hind legs
grass frog: a common semiterrestrial European frog

true frog (noun)	grass frog (noun)
insectivorous usually semiaquatic web-footed amphibian with smooth moist skin and long hind legs	a common semiterrestrial European frog