noun, adverb
every evening; night after night
Describes something happening repeatedly each night, often with a sense of continuity or routine.
彼は夜々遅くまで仕事をしている。
He works late every night.
夜々の星空を眺めるのが好きだ。
I like gazing at the starry sky night after night.
毎晩 is the standard word for 'every night' in daily conversation; 夜々 is more literary and emphasizes repetition.
Reduplication of 夜 (よ, 'night'), forming an adverb/noun meaning 'every night' or 'night after night'.