Done versus finished. Grammar myth and its origin. "Cakes are done; people are finished?" Nope. Cakes can also be finished and people can also be done. And stop mentioning cake if you’re only teasing me.
The Washington Post Style Guide Now Accepts Singular They
What do you do when you run into your friend on their birthday? You wish them a happy birthday, of course! Or wait—you wish … him or her a happy birthday? When you run into your friend on … his or her birthday? That's how you’re supposed to say it if you want to avoid using they to refer to one person, but it’s a bit wordy and awkward.