mournful

Mournful means full of sorrow, or expressing it. A face, a tune, the sound of a foghorn.

The word describes appearance and sound more than the feeling itself, so a mournful expression and a mournful howl are its natural homes. Animals get it constantly in writing, since a dog left alone sounds mournful. It is gentler and more decorative than grief-stricken, and it can be used with light affection about somebody merely gloomy. Behind it sits mourning, the formal period of grief after a death.