noun
penance; austerity; difficult practice
Primarily a Buddhist term for rigorous spiritual training or ascetic practice, often involving hardship. Can also refer more broadly to any difficult undertaking or ordeal.
彼は山にこもって難行を続けた。
He secluded himself in the mountains and continued his penance.
この修行はまさに難行だ。
This training is truly a difficult practice.