Here's why:
* It describes a noun: It tells us something about a person, place, or thing. For example:
* "The innocent child was unaware of the danger."
* "The innocent bystander was caught in the crossfire."
* It can be modified by adverbs: We can add words like "completely" or "very" to describe the degree of innocence. For example:
* "He was completely innocent of the crime."
While "innocent" can sometimes be used as a noun (meaning "someone who is not guilty"), its primary function is as an adjective.