It’s THEY. Why would that have been chosen as the WOTY? Everyone knows what they means, don’t they? Look at that last sentence I wrote: Everyone is singular and they is a plural pronoun. Not so long ago, that would have been considered a grammatical error. However, it’s very common for people to use that “incorrect” construction, the singular they, in speech and in everyday informal writing.
But Merriam-Webster is calling attention to this use of they for a serious reason. The LGBTQ community has been advocating for an inclusive pronoun that does not refer to any specific gender. Trans people are troubled by the use of he and him or she and her; Jamie may have been assigned one gender at birth but later transitioned to another gender. Do we refer to Jamie as she or as he? Or is Jamie gender-fluid? Sometimes, Jamie may even be referred to by the de-humanizing pronoun it.
To be respectful of the variety of human identity and sexual orientations, they has been adopted to represent everyone. If you don’t know what pronoun a person prefers, my thinking is that they would welcome you asking them.
Language changes. All languages change. Shakespeare, Chaucer, and Emily Dickinson all used they/them/their in their writing when referring to one person. But then The Grammarians (you know, people like me) insisted on strict pronoun agreement: singular with a singular referent, plural with plural. I no longer do. If a person is comfortable using they as their pronoun, I respect that. I hope you’ll think about what making this small gesture might mean to that person.