rudus

The term "rudus" refers to a layer of concrete used in Roman road construction. This layer, typically about 9 inches thick, was made from stones smaller than 2 inches in size. It was part of a sophisticated construction method where Roman roads were built in straight lines, often overcoming significant geographical obstacles. The Romans, drawing expertise from various cultures, utilized concrete extensively, enabling them to build approximately 53,000 miles of roads across their empire for military, economic, and administrative purposes. The Appian Way, begun in 312 BCE, is a famous example of their extensive road-building efforts. The adjective "ruderal" describes plants that grow in disturbed areas, a term derived from the Latin word for rubble.12