crawdad vs decapod

crawdad and decapod both are nouns.

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

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

crawdad: small freshwater decapod crustacean that resembles a lobster
decapod: crustaceans characteristically having five pairs of locomotor appendages each joined to a segment of the thorax

Other hypernyms of crawdad include decapod crustacean.

crawdad (noun)	decapod (noun)
small freshwater decapod crustacean that resembles a lobster	crustaceans characteristically having five pairs of locomotor appendages each joined to a segment of the thorax
tiny lobster-like crustaceans usually boiled briefly	cephalopods having eight short tentacles plus two long ones