規定
きてい · kitei · JLPT N1 · noun
regulation
規 (rule, measure) + 定 (fix, settle) = a rule that is fixed and settled
規 means a rule or standard; 定 means to decide or set. Together they name the rules that have been decided and set down. Read it as 'rule + settle' to recall the meaning.
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.'