九 kyuu vs ku

きゅう vs く

きゅう is the safe default (counting, age) while く is a specialized variant used for month (September: kugatsu くがつ), time (9 o’clock: くじ), and certain counter words (The 9th of a month is kokonoka ここのか).

Created July 9, 2026
Last edited July 9, 2026