留める

1. Origins, structure, and basic meaning

• Structure: 留める (とめる) adds okurigana める to keeping 留, forming a transitive verb.
• Basic usage: It describes fastening papers and retaining words in one's mind.

2. Common pitfalls and similar expressions

• Physical fastening and mental retention
  • A clip gives the literal sense, while 心に留める means deliberately keeping an idea or warning in memory.