An i-adjective that means futile, vain, or empty. It expresses a sense of emptiness or hollowness, often after an effort has proven to be pointless or has failed to produce any meaningful result. It can refer to a futile effort (空しい努力) or a general feeling that life is meaningless (人生が空しい). Example: "After his team lost the final match, all his hard training felt futile."

努力や行為に価値や意味がなく、虚しい気持ちになる様子を表すい形容詞。中身がなく、空っぽである状態も指す。「空しい努力」「空しい人生」のように使う。例文：「一生懸命説得したが、彼の心には響かず空しかった。」