Singular:
* Noun: cat
* Pronoun: it
Plural:
* Noun: cats
* Pronoun: they
Other examples:
* Noun: book
* Pronoun: it
* Plural: books
* Pronoun: they
* Noun: flower
* Pronoun: it
* Plural: flowers
* Pronoun: they
* Noun: child
* Pronoun: it
* Plural: children
* Pronoun: they
Important Note: Pronouns often replace nouns to avoid repetition. The pronoun must agree in number (singular or plural) with the noun it replaces.