Melancholia is both an outdated term for depression itself and, currently, a clinically defined characteristic of major depression listed in the Diagnostic and Statistical Manual of Mental Disorders.

The term "melancholia" is derived from the Greek words melas, meaning black, and chole, meaning bile, and is a vestige of the ancient belief that a person's health and temperament are determined by the relative proportions of the four cardinal humors, or body fluids, which are blood, phlegm, choler (yellow bile), and melancholy (black bile). The central feature of melancholic depression is persistent and unremitting sadness. Persons suffering from this disorder are unable to enjoy normally pleasurable experiences, even brief ones, and they...