Topic: Composition,

Best Answer Explained in Below-:

A preposition is considered a "relating word" because it establishes relationships between different elements within a sentence, particularly between nouns or pronouns and other words. Prepositions help indicate various relationships, such as time, place, direction, and manner, by linking the objects they govern to other components in the sentence. For example, in the phrase "The book is on the table," the preposition "on" relates the noun "book" to the noun "table," indicating the spatial relationship between them.

While "qualifying," "joining," and "modifying" could describe other parts of speech or functions, they don't accurately capture the primary role of prepositions. Qualifying and modifying typically pertain to adjectives and adverbs that describe or limit meaning, while joining is more characteristic of conjunctions that connect clauses or sentences. Thus, "relating word" is the most appropriate description, as it emphasizes the fundamental role of prepositions in defining how nouns and pronouns are conceptually positioned in relation to other sentence elements.