Here's why:
* It names a concept: Inequality refers to the state of being unequal, which is an abstract idea.
* It can be the subject or object of a sentence:
* "Inequality is a serious problem in our society." (subject)
* "We should fight against inequality." (object)
However, it can sometimes be used as an adjective, though this is less common:
* Example: "The inequality of wealth distribution is alarming."
Therefore, "inequality" is primarily a noun, but can be used as an adjective in certain contexts.