筒

1. Origins, structure, and basic meaning

• Structure: 筒 is read つつ and refers to a long, hollow tube.
• Basic usage: It describes a tube holding rolled paper or a tube shape made from paper.

2. Common pitfalls and similar expressions

• Shape and material
  • 筒 names a form, not a particular material such as paper or metal. Unlike 箱, a box, 筒 focuses on a long, tubular structure.