polychaete vs lobworm

polychaete and lobworm both are nouns.

Word	Noun	Adjective	Verb	Adverb
polychaete	Yes	No	No	No
lobworm	Yes	No	No	No

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

polychaete: chiefly marine annelids possessing both sexes and having paired appendages (parapodia) bearing bristles
lobworm: marine worms having a row of tufted gills along each side of the back; often used for fishing bait

Other hyponyms of polychaete include lug, lugworm, sea mouse, bloodworm.

polychaete (noun)	lobworm (noun)
chiefly marine annelids possessing both sexes and having paired appendages (parapodia) bearing bristles	marine worms having a row of tufted gills along each side of the back; often used for fishing bait