What part of speech is forest?

"Forest" can be either a noun or an adjective, depending on how it's used in a sentence.

Noun:

* "We walked through the forest." Here, "forest" is the object of the preposition "through" and is a noun.

Adjective:

* "The forest floor was covered in leaves." Here, "forest" modifies the noun "floor" and acts as an adjective.