Several parts combine into one character.

季 is a compound ideograph: 禾 (a stalk of grain — millet or rice with drooping head) + 子 (child / young one). The composite captures "young grain" — the early-stage rice or millet that marks the beginning or end of an agricultural cycle. From this concrete agricultural origin grew the abstract sense "season / period / cyclical time." A second meaning emerged from family hierarchy: classical Chinese ranked siblings as 伯 (eldest), 仲 (second), 叔 (third), 季 (youngest) — the youngest sibling held the 季 position. So 季 carries both seasonal and "youngest in birth order" senses.

Korean reading "gye." 季節 (gyejeol, season — universal Korean term for the four seasons), 四季 (sagye, four seasons), 秋季 (chugye, autumn season — used in "fall sports day"), 夏季 (hagye, summer season), 季刊 (gyegan, "seasonal publication" = quarterly journal), 伯仲叔季 (baekjung-sukgye, the four classical sibling positions — referenced in literary and historical writing about family hierarchies).

Mandarin jì, 4th tone. 季节 (jìjié, season), 四季 (sìjì, four seasons), 季度 (jìdù, quarter — fiscal/business quarters: 第一季度 first quarter), 赛季 (sàijì, "competition season" = sports season — used for soccer leagues, NBA, e-sports: NBA赛季). The compound 赛季 entered Mandarin as Western sports leagues entered the country, becoming standard sports vocabulary.

Japanese on-reading キ (ki) — 季節 (kisetsu, season), 四季 (shiki, four seasons — central to Japanese aesthetics), 夏季 (kaki, summer season), 冬季 (tōki, winter season — used in 冬季オリンピック "Winter Olympics"), 季刊 (kikan, quarterly publication). Japan's reverence for seasonal awareness elevates 四季 (shiki) to central cultural status: traditional poetry forms like haiku require seasonal kigo (季語), traditional cuisine emphasizes 旬 (shun, peak-season ingredients), and tea ceremony explicitly seasonalizes its utensils and motifs. Vivaldi's Four Seasons in Japanese is simply 四季 (Shiki), no further translation required — the concept is already deeply Japanese.

Memory aid: young grain (禾 + 子) — the seasonal cycle marked by rice growing.