HSK 7-9
乐此不疲
lècǐ-bùpí(idiom) to enjoy sth and never tire of it
他研究古地图多年仍乐此不疲。
Tā yánjiū gǔ dìtú duōnián réng lècǐ-bùpí.
He has studied old maps for years without ever tiring of it.
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Appears across levels (7-9) in the HSK 3.0 word list.