noun
another thought; distraction
Almost exclusively used in the set phrase 余念がない, meaning 'to be completely absorbed in something with no room for other thoughts'. Rarely appears outside this negative construction.
彼は研究に余念がなかった。
He was completely absorbed in his research.
子供たちは遊びに余念がない。
The children are totally engrossed in their play.
Compound of 余 (extra, remaining) and 念 (thought, sense). The literal meaning is 'remaining thought', which developed into the idea of having no other thoughts when used in the negative.