改定
かいてい · kaitei · JLPT N1 · noun
reform
改 — 己 (self) + 攴/攵 (action/strike)
改 is a compound of 己 'self' and 攵 (the action radical, originally a hand holding a stick). The image is of striking or applying force to oneself or one's situation, suggesting reform or correction. From this came the modern meaning 'to change, alter, correct'.
定 — roof 宀 + 正 (correct/upright, phonetic)
Originally written with 宀 (roof) over 正 (upright/correct), suggesting a household settled and orderly under its roof. Over time 正 simplified to 㐬-like form at the bottom, and the meaning shifted from 'settled home' to the broader senses of 'fix, stable, decide.'