* Noun: This is the most common usage. A paradox is a statement that, despite apparently valid reasoning from true premises, leads to a seemingly self-contradictory or logically unacceptable conclusion.
* Example: "This statement is false." (If it's true, it's false, and if it's false, it's true.)
* Adjective: This is less common, but still valid. It means something that is self-contradictory, seemingly impossible, or absurd.
* Example: "The paradoxical nature of time."
So, depending on the context, "paradox" can be either a noun or an adjective.