Mourning (n.) is a condition in which the world has become poor and empty... melancholia is a condition in which it is the ego itself that has become poor and empty.
Mourning (n.) is not overcome by attaching to a new love object, but by slow-going reality-testing which reveals to the ego that the love object no longer exist, thus requiring that libidinal investments be slowly withdrawn from it through the painful work of mourning.
Mourning (n.) is not simply an emotion but the performance of a trauerarbeit, or 'sorrow work': Mourning, like interpretation, is an activity.
Mourning (n.) is the healthy and appropriate way to deal with grief, marked by profoundly painful dejection, cessation of interest in the outside world, loss of the capacity to love, and, inhibition of all activity.
Mourning (n.) is the poverty of the world. Melancholy is the poverty of the self in the world.