Melancholia (noun)

A state of depression characterized by feelings of sadness, hopelessness, and despair.

Origin:

From the greek μελαγχολία (melancholia) meaning "black bile", from μέλας (melas) meaning "black" and χολή (cholē) meaning "bile" or "gall".

Examples:

1. The artist's melancholia was reflected in his paintings.
2. He was suffering from melancholia after the death of his wife.
3. The melancholic mood was prevalent throughout the city.
4. She had been in a state of melancholia for weeks.
5. His melancholic demeanor made it clear that he was not okay.