鉄粉

1. Origins, structure, and basic meaning

• Structure: 鉄粉 (てっぷん) is a compound noun for fine iron particles produced through grinding or metalwork.
• Basic usage: 鉄粉が一列に並ぶ makes filings responding to a magnet the subject, while 残った鉄粉を刷毛で集める makes workbench residue the object swept together.

2. Common pitfalls and similar expressions

• Magnetic response and workshop residue
  • 鉄粉が並ぶ concerns particle arrangement, whereas 鉄粉を集める gathers dispersed powder. The noun is neither a lump of iron nor a rust stain.