For any editor or language buff who has struggled with sentences like these:
- Everyone took his or her seat.
- Your client may want his or her options increased.
The old rule, much disputed, said: If your antecedent (the word to which your pronoun refers) is singular, you cannot use the word “their” because it is plural. You have to use a singular pronoun, which was always masculine until recently (when the “his or her” construction became popular to indicate that, in the first sentence above, women sat down, too).
The good news: The American Dialect Society just named “they” (and by extension, the possessive plural “their”) as their Word of the Year (WOY).
What this means for you as a writer: Erase everything you’ve ever been taught about this aspect of pronoun agreement.
It’s going to be a good year!