prawn vs river prawn

prawn and river prawn both are nouns.

Word	Noun	Adjective	Verb	Adverb
prawn	Yes	No	Yes	No
river prawn	Yes	No	No	No

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

prawn: shrimp-like decapod crustacean having two pairs of pincers; most are edible
river prawn: large (a foot or more) edible freshwater prawn common in Australian rivers

Other hyponyms of prawn include long-clawed prawn, Palaemon australis.

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

prawn (noun)	river prawn (noun)
shrimp-like decapod crustacean having two pairs of pincers; most are edible	large (a foot or more) edible freshwater prawn common in Australian rivers
any of various edible decapod crustaceans	large Australian prawn

prawn (verb)	river prawn (verb)
fish for prawns