Traditional: 業餘
业余 (yè yú) means “in one's spare time; outside working hours; amateur (historian etc)”. It is an HSK 5 Chinese word (traditional 業餘) in the HSK 3.0 vocabulary.
我在业余时间学中文。
Wǒ zai yèyú shíjiān xué Zhōngwén.
I study Chinese in my free time.
Updated: