What part of speech is unchallenged it a noun verbpronounadverbadjective conjunction preposition or interjection?

Here's why:

* It describes a noun: It tells us something about a noun, like "His claim was unchallenged."

* It can't stand alone: It needs a noun to modify. You can't say "Unchallenged is true."

Let me know if you have any other words you'd like to identify!