ink

1. Origins, structure, and basic meaning

• Structure: 墨 means an ink stick or ink; its kun-reading is すみ and its on-reading is ぼく.
• Basic usage: 墨(すみ) can mean an ink stick or ink, while 墨汁(ぼくじゅう) means liquid ink.

2. Common pitfalls and similar expressions

• Grinding an ink stick and a drop of ink
  • 墨をすり means grinding an ink stick. 墨が一滴落ちた means that a drop of ink fell from a brush tip; 墨 covers both the solid stick and liquid ink.
  • 墨汁 applied to a brush or spilled in a drop on a desk is also liquid ink. In liquid contexts, the two words overlap.