Here's why:
* Noun: A word that names a person, place, thing, or idea. "Noun" itself is a word that names a part of speech.
* Pronoun: A word that replaces a noun (e.g., he, she, it, they).
* Verb: A word that describes an action or state of being (e.g., run, jump, think, exist).
Let me know if you'd like more examples or have any other grammar questions!