cuttlefish vs decapod

cuttlefish and decapod both are nouns.

Word	Noun	Adjective	Verb	Adverb
cuttlefish	Yes	No	No	No
decapod	Yes	No	No	No

As nouns, decapod is a hypernym of cuttlefish; that is, decapod is a word with a broader meaning than cuttlefish:

cuttlefish: ten-armed oval-bodied cephalopod with narrow fins as long as the body and a large calcareous internal shell
decapod: cephalopods having eight short tentacles plus two long ones

cuttlefish (noun)	decapod (noun)
ten-armed oval-bodied cephalopod with narrow fins as long as the body and a large calcareous internal shell	crustaceans characteristically having five pairs of locomotor appendages each joined to a segment of the thorax
	cephalopods having eight short tentacles plus two long ones