littleneck clam vs quahog

littleneck clam and quahog both are nouns.

Word	Noun	Adjective	Verb	Adverb
littleneck clam	Yes	No	No	No
quahog	Yes	No	No	No

As nouns, quahog is a hypernym of littleneck clam; that is, quahog is a word with a broader meaning than littleneck clam:

littleneck clam: a young quahog
quahog: an edible American clam; the heavy shells were used as money by some American Indians

Other hypernyms of littleneck clam include hard-shell clam, hard clam, Mercenaria mercenaria, quahaug, round clam, Venus mercenaria.

As nouns, quahog is a hypernym of littleneck clam; that is, quahog is a word with a broader meaning than littleneck clam:

littleneck clam: a quahog when young and small; usually eaten raw; an important food popular in New York
quahog: Atlantic coast round clams with hard shells; large clams usually used for chowders or other clam dishes

Other hypernyms of littleneck clam include hard-shell clam, quahaug, round clam.

littleneck clam (noun)	quahog (noun)
a young quahog	an edible American clam; the heavy shells were used as money by some American Indians
a quahog when young and small; usually eaten raw; an important food popular in New York	Atlantic coast round clams with hard shells; large clams usually used for chowders or other clam dishes