Here's why:
* Common nouns refer to general things or people (e.g., dog, city, teacher).
* Adverbs modify verbs, adjectives, or other adverbs, indicating how, when, where, or to what extent something happens.
"Everywhere" tells us where something is or happens.
For example:
* The dog is everywhere. (Here, "everywhere" modifies the verb "is" and tells us where the dog is.)
Let me know if you have any other words you'd like to categorize!