This is a small point, but I see it so often that I feel it needs to be addressed. Pronouns don’t replace nouns. They replace noun phrases (or determiner phrases, if you’re doing that kind of syntax). That means other stuff like the article and the adjectives. For example:
A fat greasy American guy sat next to me on the bus.
Suppose I want to replace the subject with the pronoun he. If it were true that pronouns replaced just nouns, then it would be grammatical to say this:
*A fat greasy he sat next to me on the bus.
But that’s clearly wrong. Instead, we’d say:
He sat next to me on the bus.
And replace all of a fat greasy American guy with he.
Sometimes the noun phrase can contain entire clauses and the pronoun would still replace the whole thing, as in:
[A dolphin [who had been rescued from an oil spill] [which occurred near Japan]] performed a trick.
She performed a trick.
And similarly, I find it odd when people say that adjectives can be used to modify pronouns. This can’t be so, because the adjectives are replaced along with the noun, so they can’t stick around to modify the pronoun. And even if you try and add adjectives, it doesn’t work.
The yellow car crashed.
*The yellow it crashed.
*Yellow it crashed.
The tall woman is famous.
She is famous.
*The tall she is famous.
*Tall she is famous.
(Click here if you don’t know what the * symbol means)