研ぐ

1. Origins, structure, and basic meaning

• Structure: 研ぐ is read as とぐ and can mean “to sharpen” or “to polish”, depending on context.
• Basic usage: The examples show sharpening a small knife and polishing a stone surface.

2. Common pitfalls and similar expressions

• Distinguishing senses and uses
  • It means sharpening an edge or polishing a surface, with the object and purpose determining the sense.