短期
たんき · tanki · JLPT N2 · na-adj
short term
⏳ 短 (short) + 期 (period) = a short period of time, so short term
The opposite is 長期 (choki, long term). 長 means long, so swap 短 for 長 to get the opposite meaning.
短 — arrow 矢 + bean/vessel 豆
Originally a phono-semantic compound: 矢 (arrow) gives the meaning, since arrows were used as a short measuring stick, while 豆 (an ancient stemmed vessel) supplied the sound. From 'short in length' the meaning broadened to 'short' in time, stature, or quality.
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.