Here's why:
* Prepositions show the relationship between a noun or pronoun and another word in the sentence. They typically indicate location, time, direction, or manner. Examples include "on," "in," "at," "to," "from," "by," "with," etc.
* Adjectives describe nouns or pronouns. They tell us more about the quality, quantity, or appearance of something. "Lovely" describes something that is beautiful or pleasing.
Example:
* Preposition: "The book is on the table." ("On" shows the location of the book)
* Adjective: "She has a lovely smile." ("Lovely" describes the smile)