crab vs Dungeness crab

crab and Dungeness crab both are nouns.

Word	Noun	Adjective	Verb	Adverb
crab	Yes	No	Yes	No
Dungeness crab	Yes	No	No	No

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

crab: decapod having eyes on short stalks and a broad flattened carapace with a small abdomen folded under the thorax and pincers
Dungeness crab: small edible crab of Pacific coast of North America

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

crab (noun)	Dungeness crab (noun)
a stroke of the oar that either misses the water or digs too deeply	small edible crab of Pacific coast of North America
decapod having eyes on short stalks and a broad flattened carapace with a small abdomen folded under the thorax and pincers	flesh of Cancer magister (Dungeness crab)
a louse that infests the pubic region of the human body
the edible flesh of any of various crabs
a quarrelsome grouch

crab (verb)	Dungeness crab (verb)
complain
fish for crab
scurry sideways like a crab
direct (an aircraft) into a crosswind