fish vs crab

fish and crab both are nouns.

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

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

Other hyponyms of fish include seine, scallop, scollop, rail, brail, angle, shrimp, net fish, shark, trawl, still-fish, prawn.

fish (noun)	crab (noun)
any of various mostly cold-blooded aquatic vertebrates usually having scales and breathing through gills	a stroke of the oar that either misses the water or digs too deeply
the flesh of fish used as food	decapod having eyes on short stalks and a broad flattened carapace with a small abdomen folded under the thorax and pincers
	a louse that infests the pubic region of the human body
	the edible flesh of any of various crabs
	a quarrelsome grouch

fish (verb)	crab (verb)
catch or try to catch fish or shellfish	complain
seek indirectly	fish for crab
	scurry sideways like a crab
	direct (an aircraft) into a crosswind