Which part of speech is used to describe a noun?

The answer is an adjective, as adjectives specifically serve the purpose of describing or modifying nouns. By providing additional information about a noun, such as its qualities, quantities, or characteristics, adjectives help to create a clearer picture in the reader's mind. For example, in the phrase "the tall building," the adjective "tall" describes the noun "building," giving the reader a better understanding of its height.

In contrast, the other parts of speech listed have different functions: verbs express actions or states of being, nouns identify people, places, things, or concepts, and adverbs modify verbs, adjectives, or other adverbs. Therefore, only adjectives are directly tied to the description of nouns, making them the correct choice for this question.