The noun "darkness" is a common, uncountable (mass)
noun; a word for a thing.
The noun 'darkness' is a concrete noun as a word for a
partial or complete absence of light; …a word for an intensity of a
color; a word for a physical property of something.
The noun 'darkness' is an abstract noun as a word for
evil or wickedness; a word for unhappiness, sadness, lack of hope;
a word for secrecy or mystery; as a synonym for night; a word for a
concept or an emotion.