期間
きかん · kikan · JLPT N3 · noun
time period
📅⏳ 期間 = period (期) + interval (間): a span of time
期 means a set time, as in 学期 (school term). 間 means the gap between two points, as in 時間 (time). Put together, a set gap of time: a period or term. Sound hook: kikan sounds like key can, as in the key can only be used during the rental period.
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.