noun

Shellfish is a broad term that refers to aquatic animals with shells, typically used for food. This category includes two main types: crustaceans and mollusks.  The crustaceans have a hard exoskeleton and include species like crabs, lobsters, shrimp, and crayfish. While the mollusks, this group includes bivalves (such as clams, oysters, and mussels, which have two hinged shells), gastropods (like snails, which typically have a single, often spiraled shell), and cephalopods (such as octopus and squid, which have a reduced or internal shell).

Example

1. For dinner, they served a variety of shellfish including shrimp and mussels.
2. He learned that he was allergic to shellfish after trying crab for the first time.
3. The seafood market had a special on shellfish, so she bought some oysters and clams.