Melancholy (n.) is marked by the fact that, in contrast to mourning where a loss is recognized and painfully dealt with, the loss in melancholia remains unconscious. The melancholic is unaware that any loss has occurred.
Melancholy (n.) is the inability to complete the work of mourning because the libidinal investments that would normally detach to become free for other investments are turned inward and attach to the ego itself.
Melancholy (n.) is a thing which, when encountering, we ought to look for a special attachment to someone in the person's life lying behind these feelings.
Melancholy (n.) is the poverty of the self in the world. Mourning is the poverty of the world.
Melancholy (n.) is the same withdrawal from the world and dejection as in mourning, but accompanied by self-reproaches and self-revilings, culminating in a delusional expectation of punishment.