decapod vs squid

decapod and squid both are nouns.

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

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

decapod: cephalopods having eight short tentacles plus two long ones
squid: widely distributed fast-moving ten-armed cephalopod mollusk having a long tapered body with triangular tail fins

Other hyponyms of decapod include cuttle, cuttlefish, spirula, Spirula peronii.

decapod (noun)	squid (noun)
crustaceans characteristically having five pairs of locomotor appendages each joined to a segment of the thorax	widely distributed fast-moving ten-armed cephalopod mollusk having a long tapered body with triangular tail fins
cephalopods having eight short tentacles plus two long ones	(Italian cuisine) squid prepared as food