octopod vs octopus

octopod and octopus both are nouns.

Word	Noun	Adjective	Verb	Adverb
octopod	Yes	No	No	No
octopus	Yes	No	No	No

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

octopod: a cephalopod with eight arms but lacking an internal shell
octopus: bottom-living cephalopod having a soft oval body with eight long tentacles

Other hyponyms of octopod include devilfish, Argonaut, Argonauta argo, nautilus, paper nautilus.

octopod (noun)	octopus (noun)
a cephalopod with eight arms but lacking an internal shell	bottom-living cephalopod having a soft oval body with eight long tentacles
	tentacles of octopus prepared as food