Other forms: downs; downed
The adverb down means "from a higher place to a lower one," like when a person climbs down a ladder or a waiter puts a tray full of cakes down on a table.
Anything that moves lower — in height, location, or volume — is down, so you can travel down south, tell your dog to get down, or turn your loud music down. Down can also refer to a mood or condition; if you're feeling down, you're sad, and if your computer is down, it's not working. Another meaning of down is the soft feathers of a young bird, which is sometimes used to fill coats or comforters.