A homonym is a word that is said or spelled the same way as another word but has a different meaning. “Bow” and “bow,” “write” and “right,” “desert and “desert” — each one of these words is a homonym.
Homonym traces back to the Greek words homos, meaning “same,” and onuma, meaning “name.” So a homonym is sort of like two people who have the same name: called the same thing but different. A homonym can be a word that sounds the same as something else — like by (“near”) and buy (“purchase”) — or it can be spelled exactly the same way and pronounced differently — like minute (unit of time) and minute (“tiny”).