clam vs soft-shell clam

clam and soft-shell clam both are nouns.

Word	Noun	Adjective	Verb	Adverb
clam	Yes	No	Yes	No
soft-shell clam	Yes	No	No	No

As nouns, soft-shell clam is a hyponym of clam; that is, soft-shell clam is a word with a more specific, narrower meaning than clam:

clam: burrowing marine mollusk living on sand or mud; the shell closes with viselike firmness
soft-shell clam: an edible clam with thin oval-shaped shell found in coastal regions of the United States and Europe

As nouns, soft-shell clam is a hyponym of clam; that is, soft-shell clam is a word with a more specific, narrower meaning than clam:

Other hyponyms of clam include hard-shell clam, quahaug, quahog, round clam, long-neck clam, steamer, steamer clam.

clam (noun)	soft-shell clam (noun)
burrowing marine mollusk living on sand or mud; the shell closes with viselike firmness	an edible clam with thin oval-shaped shell found in coastal regions of the United States and Europe
flesh of either hard-shell or soft-shell clams	a clam that is usually steamed in the shell
a piece of paper money worth one dollar

clam (verb)	soft-shell clam (verb)
gather clams, by digging in the sand by the ocean