Other forms: desideria
In literary contexts, you might read that a character experiences desiderium, a heartfelt yearning for someone or something that is gone. The word desiderium carries a sense of sadness, nostalgia, and perhaps regret.
Desiderium is a word borrowed from Latin. An example of desiderium is wishing for "the gold old days" of your early childhood. It could also be missing a bygone era, a past love, or a place from your past with which you have a strong connection. In addition to the feeling of longing itself, the word desiderium is occasionally used figuratively for that which is missed, especially an abstract concept like youth or a spirit of camaraderie among friends.