Brutalism is an architectural style characterized by rigid geometry, heavy massing, and its chief material, poured concrete. It is an expression of Modern architecture in the 20th century that privileges function and form equally, and Brutalism has also become an expression—or perhaps a symptom—of post-World War II urban renewal in England, France, Belgium, Japan, and the United States. As a term, it was coined by the architects Alison and Peter Smithson as what they called a design "ethic" (rather than an aesthetic) for functional and inexpensive housing in the 1950s, but it was popularized by the architecture critic Reyner Banham as "New Brutalism."