In the sentence "The horse ran down the street," what part of speech is "the"?

In the sentence "The horse ran down the street," "the" functions as an article. Articles are a specific type of determiner used to define the noun they precede, providing information about definiteness. In this case, "the" indicates that the noun "horse" is specific or known. This is a key characteristic of articles, as they help convey whether we are speaking about a particular instance of a noun (definite article) or in a more general sense (indefinite article). In contrast, nouns name people, places, things, or ideas; prepositions show relationships between elements in a sentence; and verbs indicate actions or states of being. Therefore, "the" is correctly classified as an article in this context.