cephalopod mollusk vs mollusk

cephalopod mollusk and mollusk both are nouns.

Word	Noun	Adjective	Verb	Adverb
cephalopod mollusk	Yes	No	No	No
mollusk	Yes	No	No	No

As nouns, mollusk is a hypernym of cephalopod mollusk; that is, mollusk is a word with a broader meaning than cephalopod mollusk:

cephalopod mollusk: marine mollusk characterized by well-developed head and eyes and sucker-bearing tentacles
mollusk: invertebrate having a soft unsegmented body usually enclosed in a shell

Other hypernyms of cephalopod mollusk include mollusc, shellfish.

cephalopod mollusk (noun)	mollusk (noun)
marine mollusk characterized by well-developed head and eyes and sucker-bearing tentacles	invertebrate having a soft unsegmented body usually enclosed in a shell