noun
Describes a person, effort, or situation as lacking value or being beyond hope. Often used in set phrases like 甲斐なしの人生 or 甲斐なしな奴.
彼は甲斐なしの人生を送った。
He led a worthless life.
そんな甲斐なしな考えは捨てろ。
Throw away such hopeless thoughts.
Compound of 甲斐 (かい, 'worth, effect') and なし ('without'). The exact historical derivation is uncertain, but the word has been used since classical Japanese to express futility or lack of value.