If the teacher is talking, don’t interrupt them.
If the teacher is talking, don’t interrupt him or her.
Correct, if somewhat clunky.
In the effort to be gender neutral, too many writers break the bonds of correct usage and resort to using a plural pronoun with a singular noun.
His or her (singular)
Better to rewrite the sentence:
If the teacher is talking, it’s best not to interrupt.
It’s a simple rule that everyone needs to learn:
Singular noun requires a singular pronoun.
And that brings us to one of those tricky parts of the rule:
Everyone needs their umbrella today.
Everyone needs his or her umbrella today.
Indefinite pronouns (such as everyone, everybody, everything, someone, somebody, something etc) are singular and require a singular pronoun.
Everyone is happy. (Not Everyone are happy).
Everything has its place. (Not Everything has their place).
And the trickiest of all the indefinite pronouns in “none”.
None of the cars is washed.
None is washed.
I know, I know. You’re dying to say “None ARE washed.” Well, go ahead. But you would be grammatically incorrect.
It’s a minefield, but you can remember it this way:
Indefinite pronouns that end in “one”, “body” or “thing” are singular. One. Replace the word with a singular pronoun like “her” or “he” or “it” and test it.
Everyone had their umbrella becomes,
He had their umbrella. (Hunh?)
Pay attention now, and see how often newspapers, broadcasters and the general public get it wrong.
Pronoun agreement. A grammer geek’s dream!