chiton vs mollusc

chiton and mollusc both are nouns.

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

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

chiton: 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 chiton include mollusk, shellfish.

chiton (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
a woolen tunic worn by men and women in ancient Greece