太い

1. Origins, structure, and basic meaning

• Structure: 太い is read as ふとい and can mean “thick” or “wide”, depending on context.
• Basic usage: The examples show a thick pencil and a pillar much wider than an arm.

2. Common pitfalls and similar expressions

• Distinguishing senses and uses
  • It describes a large diameter or line width; 厚い is more natural for the front-to-back thickness of a board or book.