crab vs stone crab

crab and stone crab both are nouns.

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

As nouns, stone crab is a hyponym of crab; that is, stone 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
stone crab: large edible crab of the southern coast of the United States (particularly Florida)

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

crab: the edible flesh of any of various crabs
stone crab: pale flesh with delicate texture and flavor; found in Florida but now very rare

crab (noun)	stone crab (noun)
a stroke of the oar that either misses the water or digs too deeply	large edible crab of the southern coast of the United States (particularly Florida)
decapod having eyes on short stalks and a broad flattened carapace with a small abdomen folded under the thorax and pincers	pale flesh with delicate texture and flavor; found in Florida but now very rare
a louse that infests the pubic region of the human body
the edible flesh of any of various crabs
a quarrelsome grouch

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