hard clam vs quahog

hard clam and quahog both are nouns.

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

As nouns, hard clam and quahog are synonyms defined as:

hard clam and quahog: an edible American clam; the heavy shells were used as money by some American Indians

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

hard clam (noun)	quahog (noun)
an edible American clam; the heavy shells were used as money by some American Indians	an edible American clam; the heavy shells were used as money by some American Indians
	Atlantic coast round clams with hard shells; large clams usually used for chowders or other clam dishes