Cuttlefish and Mollusk

Cuttlefish noun - Ten-armed oval-bodied cephalopod with narrow fins as long as the body and a large calcareous internal shell.

Mollusk and cuttlefish are semantically related In some cases you can replace term "Mollusk" with "Cuttlefish", this nouns are similar.

Mollusk noun - Invertebrate having a soft unsegmented body usually enclosed in a shell.

Cuttlefish and mollusk are semantically related in invertebrate topic. You can use "Cuttlefish" instead a noun "Mollusk".