noun
shades of evening; dead of night
Literary noun for the darkness of night, often used in the phrase 夜陰に乗じて (under cover of darkness). Not an everyday word; 夜の闇 or 夜の暗がり are more common in casual speech.
See also: 夜陰に乗じて
夜陰に乗じて敵陣に忍び込んだ。
Under cover of darkness, they sneaked into the enemy camp.
犯人は夜陰に紛れて逃亡した。
The culprit fled under the cover of night.
Compound of 夜 (night) and 陰 (shade, darkness). The exact historical derivation is uncertain, but the word has been used in literary Japanese to refer to the concealing darkness of night.