Here's why:
* Nouns are words that name people, places, things, or ideas (e.g., dog, park, table, happiness).
* Pronouns are words that replace nouns (e.g., he, she, it, they).
* Determiners are words that come before nouns to specify them (e.g., a, an, the, this, that, my, your).
Example:
* A dog is playing in the park. ("Dog" is the noun, "a" is the determiner)