秋季 (qiūjì) is a noun meaning "autumn" or "fall season." It is the more formal equivalent of 秋天 (qiūtiān) and is commonly used in official, academic, or media contexts, such as describing when a TV show will air or when a school term begins.
秋季是北京最美的季节。
Qiūjì shì Běijīng zuì měi de jìjié.
Autumn is the most beautiful season in Beijing.
这部新剧预计在秋季播出。
Zhè bù xīn jù yùjì zài qiūjì bōchū.
This new drama series is expected to air in the fall.
大学秋季学期九月初正式开学。
Dàxué qiūjì xuéqī jiǔ yuè chū zhèngshì kāixué.
The university's fall semester officially starts in early September.