Recently, when I went to McDonald's, I saw on the menu that you could have an order of 6, 9, or 12 Chicken McNuggets. I asked for a half dozen nuggets. "We don't have half dozen nuggets", said the teenager at the counter.
"You don't?" I replied.
"We only have six, nine, or twelve," was the reply.
"So I can't order a half-dozen nuggets, but I can order six?"
"That's right."
So I shook my head and ordered six McNuggets.