amphipod vs sand hopper

amphipod and sand hopper both are nouns.

Word	Noun	Adjective	Verb	Adverb
amphipod	Yes	No	No	No
sand hopper	Yes	No	No	No

As nouns, sand hopper is a hyponym of amphipod; that is, sand hopper is a word with a more specific, narrower meaning than amphipod:

amphipod: a kind of malacostracan crustacean
sand hopper: small amphipod crustaceans that hop like fleas; common on ocean beaches

Other hyponyms of amphipod include beach flea, sand flea, sandhopper, skeleton shrimp, whale louse.

amphipod (noun)	sand hopper (noun)
a kind of malacostracan crustacean	small amphipod crustaceans that hop like fleas; common on ocean beaches