isopod vs woodlouse

isopod and woodlouse both are nouns.

Word	Noun	Adjective	Verb	Adverb
isopod	Yes	No	No	No
woodlouse	Yes	No	No	No

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

isopod: any of various small terrestrial or aquatic crustaceans with seven pairs of legs adapted for crawling
woodlouse: any of various small terrestrial isopods having a flat elliptical segmented body; found in damp habitats

Other hyponyms of isopod include slater, wood louse, sea louse, sea slater.

isopod (noun)	woodlouse (noun)
any of various small terrestrial or aquatic crustaceans with seven pairs of legs adapted for crawling	any of various small terrestrial isopods having a flat elliptical segmented body; found in damp habitats