Achoo is the sound people make when they sneeze. It's one of those words that sounds exactly like what it describes, called an onomatopoeia. When dust tickles your nose or bright sunlight makes you sneeze, out comes that explosive “achoo!”

Different languages have different ways of writing this sound. In Spanish, people say achís. In Japanese, it's hakushon. In French, atchoum. But they're all trying to capture that same sudden burst of air rushing out of your nose and mouth.

When you hear someone say “achoo,” people often say “bless you” or “gesundheit” (a German word meaning “health”). And if you're the one sneezing, covering your nose and mouth helps keep germs from spreading.