Prepositions are not nouns, they are words that show the relationship between a noun or pronoun and other words in the sentence.
Here's why it's not a noun:
* Concrete nouns refer to physical things you can touch (e.g., chair, tree, book). "Inside" doesn't describe a physical object.
* Abstract nouns refer to ideas, concepts, or qualities (e.g., happiness, freedom, justice). While "inside" could be used to describe a location or a concept, it's not a noun itself.
Example:
* The cat is inside the box. (Here, "inside" is a preposition showing the cat's location in relation to the box).