A Pattern Language (1977) by Christopher Alexander, Sara Ishikawa, Murray Silverstein and colleagues at the Center for Environmental Structure presents 253 interlinked design patterns, each describing a recurring problem and a tested spatial solution. The patterns are arranged hierarchically, from the scale of regions and towns down through neighbourhoods and buildings to rooms, alcoves and doorways. Each pattern is written to be combined like words in a language so that ordinary people, not only professionals, can shape humane places. The book was part of a trilogy with The Timeless Way of Building.
It was enormously influential across architecture, planning and participatory design, giving non-experts a structured way to take part in shaping their environments. Its pattern concept later spread far beyond building, notably into software engineering, where design patterns became a standard idea.