A pronoun can work as a subject.
These are the subject pronouns: she, he, we, I, you, they, it.
Subject pronouns do the action.
She can do the action. He can do the action.
We can do the action. They can do the action.
I can do the action. It can do the action.
However, it’s important to remember that a noun must appear before you can use a pronoun to replace that noun.
Here is a sentence using a subject pronoun: She will be late for work.
Because we didn’t use an antecedent first, we don’t know what noun the subject pronoun is replacing.
Now look at this sentence: Mom is out of gas, so she will be late for work.
This sentence has a noun antecedent in the first part of the sentence and a subject pronoun in the second part.
Mom is the noun antecedent, and she is the pronoun that replaces Mom.
Remember that she, he, we, I, you, they, it are subject pronouns that do the action in a sentence.
Also remember that you must use a noun as an antecedent before you can use a pronoun. Otherwise, we don’t know what noun the pronoun is replacing.