adverb
earnestly; intently; wholeheartedly
Describes doing something with complete focus, without distraction or other thoughts. Often used with verbs like 取り組む, 打ち込む, or 祈る. The variant 余念もなく is also common.
See also: 余念もなく (よねんもなく)
彼は研究に余念無く取り組んでいる。
He is earnestly engaged in his research.
選手
The players concentrated intently on the game.
Synonymous variant; 余念無く and 余念もなく are interchangeable, with 余念もなく perhaps slightly more common in modern usage.
From 余念 (other thoughts) + 無く (without). The exact historical derivation is uncertain, but the phrase is conventionally used to mean 'without distraction'.