Here's why:
* Noun: "Mountain" is a noun, a word that names a person, place, or thing.
* Adjective: "Blue" modifies the noun "mountain," describing its color.
* Phrase: The combination of "blue" and "mountain" acts as a unit, functioning as a noun in a sentence.
For example:
* "I saw a blue mountain in the distance." Here, "blue mountain" acts as the object of the verb "saw."
While "blue mountain" can also refer to a specific place or brand, in general, it functions as a noun phrase.