What is the definition of a noun?

A a word that replaces another word or phrase

B a word that expresses emotion

C a word that describes action, existence, or occurrence

D a word that names a person, place, or thing

The correct answer is D. a word that names a person, place, or thing.

Explanation:

Nouns are words that give us the names of people (John, Helen, Tom, etc.), places (courtyard, school, home, etc.), things (pencil, desk, computer, etc.). emotions (love, hate, happiness, etc.), and many other things. They usually act as subjects or objects within a sentence.

A is incorrect because that definition refers to pronoun, rather than noun. B is incorrect because nouns express so much more than just emotions. C is incorrect because that definition refers to verbs. Therefore, we are left with D.