wistful

他看着老照片，眼中流露出怀念的神情。

He looked at the old photos with a ___wistful expression in his eyes.

黄昏时分站在阳台上，随着海面上最后一抹橙色消逝，她发出一声怅然的叹息。

Standing on the balcony at dusk, she let out a ___wistful sigh as the last streaks of orange faded over the sea.

他怅然地看了一眼离站的火车，想起了他在那个海滨小镇度过的所有夏天。

He cast a ___wistful glance at the departing train, remembering all the summers he had spent in that small coastal town.