You’ve heard of indefinite pronouns—pronouns that don’t refer to a specific thing, place, or person. Examples include everybody, anything, someone, another, something, and a few others. Did you know, however, that there’s another kind of indefinite pronoun called an expletive? The English language has two such expletives: it and there.
Consider the following sentences:
It might rain tomorrow.
There wasn’t enough money to pay the rent.
In these sentences, it and there are not pronouns that refer to or replace any existing noun. Yet they’re necessary to fill in because each sentence syntactically requires a subject.
Sometimes we can’t avoid using an expletive, but if you can recast a sentence to get around it, it’s good to do so. You can expand the sentence to give it a clear subject, or if the surrounding context identifies a previous noun, you can repeat it.
The forecast calls for rain tomorrow.
Doctor bills had bled the family’s reserves. They didn’t have enough money to pay the rent.
If you have to struggle to eliminate an expletive, it’s fine to let it stand. It’s an innocuous part of speech that doesn’t jump out at readers or disrupt flow, and usually its meaning is clearly understood.