The word 遗憾 is formed by combining two characters, each contributing a layer of meaning to create a unified concept. The first character, 遗 (yí), carries the core idea of "to leave behind" or "to lose". The second, 憾 (hàn), means "regret" or "disappointment". Together, they conceptually paint a picture of a feeling that is "left-behind regret", a lingering sense of sorrow or dissatisfaction over something that has been lost, missed, or left unfulfilled.