亀甲

1. Origins, structure, and basic meaning

• Structure: 亀甲（きっこう） means a turtle or tortoise shell, or a pattern modeled on its shape.
• Basic usage: Use it for examining a shell specimen or describing a lattice pattern.

2. Common pitfalls and similar expressions

• The shell itself versus a pattern
  • 亀甲の標本 refers to a specimen of the shell itself.
  • 亀甲模様 refers to a pattern modeled on the shell's hexagonal shapes.