Here's why:
* It describes a noun: We use "phenomenal" to describe something that is extraordinary, impressive, or remarkable.
* Example: "The singer gave a phenomenal performance." (Describing the performance, a noun)
* It can be modified by adverbs:
* Example: "The movie was incredibly phenomenal." (Using the adverb "incredibly" to modify the adjective "phenomenal")
While "phenomenal" can sometimes be used as a noun (referring to a phenomenon), this is less common.