noun
dark night; moonless night
Refers to a night with no moonlight or very little light, often evoking a sense of deep darkness.
闇夜にカラスの鳴き声が響いた。
The cawing of a crow echoed through the dark night.
闇夜では足元が見えにくい。
It's hard to see your feet on a moonless night.
Compound of 闇 (yami, 'darkness') and 夜 (yo, 'night'). The reading やみよ is a straightforward combination of the kun'yomi readings.