定期
ていき · teiki · JLPT N3 · noun
term
📅 定期 = fixed (定) + period (期): a set, regular term
定 means settle or fix, as in 決定 (decision). 期 means a period of time, as in 期間 (term). Together they make a fixed or regular term, which is why 定期券 (teikiken) is a commuter pass valid for a set period.
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.'
期 — 其 (phonetic) + 月 (moon/time)
期 is a phono-semantic compound. The right side 月 (moon) signals meaning, since lunar cycles marked fixed time periods in ancient China. The left side 其 supplies the sound. Together it points to a set time, period, or appointed date — meanings still carried today in words like 期间 and 日期.