Poetic or literary term for the deepening darkness after sunset, often evoking a quiet, melancholic atmosphere.
宵闇が迫る頃、街灯がぽつりぽつりと灯り始めた。
As dusk approached, the streetlights began to flicker on one by one.
彼女は宵闇に紛れて姿を消した。
She disappeared into the twilight.
Compound of 宵 (よい, 'early evening') and 闇 (やみ, 'darkness'). The exact historical derivation is uncertain, but the word has been used in classical Japanese poetry to evoke the transition from dusk to night.