What was a water ditch dig around the outside of a castle called?

A water ditch dug around the outside of a castle is called a moat. Moats were designed to enhance the castle's defenses by creating a barrier against attackers, making it more challenging to breach the walls. They could be filled with water, mud, or even left dry, depending on the castle's location and design. Moats often served both practical defensive purposes and aesthetic functions.