A windmill is a machine which converts the energy of wind into rotational energy by means of vanes called sails or blades. Originally windmills were developed for milling grain for food production. In the course of history the windmill was adapted to many other industrial uses. An important non-milling use is to pump water, either for land drainage or to extract groundwater with windpumps. Windmills used for generating electricity are commonly known as wind turbines. The windwheel of the Greek engineer Heron of Alexandria in the 1st century AD is the earliest known instance of using a wind-driven wheel to power a machine. Another early example of a wind-driven wheel was the prayer wheel, which was used in ancient Tibet and China since the 4th century.
Contributions by Arnoutf, 188.8.131.52, and 184.108.40.206.