Cephalopod and Shellfish

Cephalopod noun - Marine mollusk characterized by well-developed head and eyes and sucker-bearing tentacles.

Shellfish and cephalopod are semantically related. In some cases you can use "Shellfish" instead a noun "Cephalopod".

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

Cephalopod and shellfish are semantically related. Sometimes you can replace term "Cephalopod" with "Shellfish", this nouns are similar.