chowder vs clam chowder

chowder and clam chowder both are nouns.

Word	Noun	Adjective	Verb	Adverb
chowder	Yes	No	No	No
clam chowder	Yes	No	No	No

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

chowder: a thick soup or stew made with milk and bacon and onions and potatoes
clam chowder: chowder containing clams

Other hyponyms of chowder include corn chowder, fish chowder.

chowder (noun)	clam chowder (noun)
a thick soup or stew made with milk and bacon and onions and potatoes	chowder containing clams