Dark
Part of speech: noun
Definition: A complete or (more often) partial absence of light. Ignorance. Nightfall.
Part of speech: adjective
Definition: Having an absolute or (more often) relative lack of light. Dull or deeper in hue; not bright or light. Hidden, secret Without moral or spiritual light; sinister, malign. Conducive to hopelessness; depressing or bleak Lacking progress in science or the arts; said of a time period With emphasis placed on the unpleasant aspects of life; said of a work of fiction, a work of nonfiction presented in narrative form or a portion of either
Example sentence: In a real dark night of the soul, it is always three o'clock in the morning, day after day.
Caliginous
Part of speech: adjective
Definition: Which is influenced by darkness or obscurity.