定期券
ていきけん · teikiken · JLPT N2 · noun
base on balls
🎫 定期 = fixed/regular + 券 = ticket: a ticket for regular, fixed-period travel
定 means fixed or set, and 期 means period. 券 is ticket, so a 定期券 is a ticket valid for a set period of repeated trips.
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.
券 — ⺉ knife radical + 龹 (phonetic top)
Originally written 券, depicting a tally cut with a knife (刀/⺉) into two halves so each party could keep proof of an agreement. The top element 龹 supplies the sound. From this 'split tally' sense it came to mean a certificate, ticket, or voucher.