What is the term for a word that relates a noun or pronoun to another word or phrase?

The correct term for a word that connects a noun or pronoun to another word or phrase is indeed a preposition. Prepositions serve to establish relationships between different elements in a sentence, often indicating direction, location, time, or manner. For example, in the phrase "The book is on the table," the word "on" is a preposition that relates the noun "book" to the noun "table," providing clarity about the position of the book.

On the other hand, verbs express actions or states of being, adverbs modify verbs, adjectives, or other adverbs often indicating how, when, where, or to what extent something occurs, and conjunctions connect words, phrases, or clauses within a sentence. Each of those choices serves a distinct function in grammar, but the specific role of linking nouns or pronouns to other words or phrases is the hallmark of a preposition.