Chiton and Shellfish

Chiton noun - Primitive elongated bilaterally symmetrical marine mollusk having a mantle covered with eight calcareous plates.

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

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

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