reform

1. Origins, structure, and basic meaning

• Structure: 改 has 7 strokes and the on-reading かい. 改める (あらためる) means to revise or arrange anew; 改まる (あらたまる) means to change or become formal.
• Basic usage: 改める describes changing wording or a date; 改まる describes a rule changing or an atmosphere becoming formal.

2. Common pitfalls and similar expressions

• Making a change and a changed state
  • 表現を改めました means revising the wording. 日を改める means choosing another day, rather than only correcting an erroneous date.
  • 規則が改まった means that a rule was revised. 雰囲気が改まった means that the atmosphere became formal.