What is a function word that combines with a noun or pronoun to form a prepositional phrase?

The correct choice is a preposition because it is a function word that links nouns or pronouns to other elements in a sentence, thereby forming a prepositional phrase. A prepositional phrase includes the preposition itself and the object of the preposition, which can be a noun or a pronoun, along with any modifiers of that object. For example, in the phrase "under the table," "under" is the preposition that connects the noun "table" to the rest of the sentence, establishing a relationship of location.

Understanding this role is critical in grammar and writing, as prepositions provide necessary detail about time, place, direction, and manner, enriching the meaning of the sentences in which they are used. This functionality distinguishes prepositions from other types of words on the list, highlighting their specific role in sentence structure and meaning.