polyplacophore vs mollusc

polyplacophore and mollusc both are nouns.

Word	Noun	Adjective	Verb	Adverb
polyplacophore	Yes	No	No	No
mollusc	Yes	No	No	No

As nouns, mollusc is a hypernym of polyplacophore; that is, mollusc is a word with a broader meaning than polyplacophore:

polyplacophore: primitive elongated bilaterally symmetrical marine mollusk having a mantle covered with eight calcareous plates
mollusc: invertebrate having a soft unsegmented body usually enclosed in a shell

Other hypernyms of polyplacophore include mollusk, shellfish.

polyplacophore (noun)	mollusc (noun)
primitive elongated bilaterally symmetrical marine mollusk having a mantle covered with eight calcareous plates	invertebrate having a soft unsegmented body usually enclosed in a shell