淡季 literally means 'light season' — 淡 (dàn) conveys 'light', 'weak', or 'low intensity', while 季 (jì) means 'season'. Together, they form a compound noun meaning 'off-season': the period when activity, demand, or business is low, especially in tourism, retail, or transportation. It contrasts directly with 旺季 (wàn jì), or 'peak season'.

This term is widely used in commercial and travel contexts to describe times of reduced visitor numbers, lower prices, and fewer crowds — for example, winter months for beach resorts or midweek days for hotels. Unlike English 'off-season', which can occasionally imply inactivity in sports or arts, 淡季 in Chinese almost always carries an economic or logistical connotation, rarely referring to biological or natural cycles like animal breeding seasons.