countdown

A countdown is when you count backwards from a certain number until zero.

You often see a countdown on TV or online before a big event, like New Year's Eve or a fireworks display. It starts with a high number and goes all the way down to one, then finally reaches zero. Sometimes, people also use it in everyday life, like when they're waiting for something exciting to happen, like their favorite sports team winning a game or getting a new phone on sale. They might start counting down the days until the event, saying "only 5 more days!" or "just one hour left!"