The Réaumur temperature scale is a historical temperature scale named after René Antoine Ferchault de Réaumur, a French scientist. It was developed in the early 18th century as an alternative to the Celsius scale.
On the Réaumur scale, the freezing point of water is defined as 0°Ré (degrees Réaumur), while the boiling point of water is set at 80°Ré. The scale divides the range between these two reference points into 80 equal parts or degrees. Hence, each degree Réaumur is 1/80th of the temperature difference between the freezing and boiling points of water.
The Réaumur scale was commonly used in parts of Europe, particularly in France and Germany, during the 18th and 19th centuries. However, it has largely been replaced by the Celsius (formerly known as Centigrade) scale, which is the modern standard for temperature measurement in most countries worldwide. In the Celsius scale, the freezing point of water is defined as 0°C, and the boiling point is set at 100°C, making it easier to relate to everyday temperature references.