Which word is usually used as an adjective?

The word "tall" is typically used as an adjective because it describes the height of a noun, providing information about a characteristic of that noun. Adjectives function to modify nouns, offering details that enhance understanding. In this case, when you use "tall," you might be talking about a tall person, a tall building, or a tall tree, giving the listener a clear visual of the height involved.

In contrast, "run" primarily operates as a verb, indicating an action. "Quickly" is an adverb that modifies verbs, adjectives, or other adverbs by describing the manner in which an action is performed. Finally, "under" functions as a preposition, indicating position or relationship between items rather than describing a noun directly. This understanding of word functions is critical for identifying adjectives in language use.