lugworm vs polychaete

lugworm and polychaete both are nouns.

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

As nouns, polychaete is a hypernym of lugworm; that is, polychaete is a word with a broader meaning than lugworm:

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

Other hypernyms of lugworm include polychaete worm, polychete, polychete worm.

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