What part of speech is challenging?

"Challenging" can be several parts of speech, depending on how it's used in a sentence:

* Adjective: This is the most common use. Example: "It was a challenging task."

* Verb: This is less common, but possible. Example: "The student challenged the teacher's explanation."

* Noun: This is even less common. Example: "The game was a real challenge."

To determine the part of speech, you need to look at the sentence and how the word is being used.