確定
かくてい · kakutei · JLPT N1 · noun
decision
確 (sure) + 定 (settle) = something made sure and settled: fixed; decision
確 means certain or firm, and 定 means to settle or set. Together they describe something that has been settled and made certain, like a fixed plan or a final decision.
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.'