Mussel and Shellfish

Mussel noun - Black marine bivalves usually steamed in wine.

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

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

Mussel and shellfish are semantically related in invertebrate topic. You can use "Mussel" instead a noun "Shellfish".