In my English-as-a-second-language class, I explained the difference between a watch and a clock.
I told the students that when it was a large timepiece on a wall and not attached to your body, it was called a clock and when it was worn on your body that it was called a watch.
A few days later we had a power outage, and our classroom clocks had not been reset.
I asked Luis, who was wearing a wristwatch, for the time.
Luis looked at his wrist, and then confidently announced,
"It is exactly ten o'watch."