甲殻

1. Origins, structure, and basic meaning

• Structure: The zoological noun 甲殻 (こうかく) is the hard outer shell or carapace of a crustacean.
• Basic usage: It is described as 硬い甲殻, and a growing shrimp can shed its old carapace.

2. Common pitfalls and similar expressions

• A hard arthropod shell
  • It is the hard protective covering of crustaceans and similar animals, not ordinary packaging or peel.