While it's not a traditional part of speech like nouns, verbs, or adjectives, prepositions are classified as function words because they don't have a lexical meaning on their own. Instead, they show the relationship between other words in a sentence, primarily nouns or pronouns.
Here's a breakdown:
* Lexical words have their own meaning (e.g., "cat," "run," "happy").
* Function words don't have their own meaning, but they help connect and structure the sentence (e.g., "of," "to," "the").
Prepositions are a type of function word that specifically show relationships of location, direction, time, or other concepts.