Sad expressions convey messages related to loss, bereavement, discomfort, pain, helplessness, etc.
Words to describe sadness:
bereaved, bitter, blue, cheerless, dejected, despairing, despondent, disconsolate, dismal, distressed, doleful, down, down in dumps, down in mouth, downcast, forlorn, gloomy, glum, grief-stricken, grieved, heartbroken, heartsick, heavyhearted, hurting, in doldrums, in grief, in the dumps, languishing, low, low-spirited, lugubrious, melancholy, morbid, morose, mournful, out of sorts, pensive, pessimistic, sick at heart, somber, sorrowful, sorry, troubled, weeping, wistful, woebegone
This is what it looks like:
A quick vid:
The Bookshelf Muse--Entry on Sadness/Grief