A castle (from Latin castellum) is a type of fortified structure built in Europe and the Middle East during the Middle Ages. Scholars debate the scope of the word castle, but usually consider it to be the private fortified residence of a lord or noble. This is distinct from a fortress, which was not a home, and from a fortified town, which was a public defence. The term has been popularly applied to structures as diverse as hill forts and country houses. Over the approximately 900 years that castles were built they took on a great many forms with many different features, although some, such as curtain walls and arrowslits, were commonplace.