About Réaumur
Réaumur was widely used in Europe in the past but is now rarely seen. The Réaumur scale was named after the French physicist René Antoine Ferchault de Réaumur who developed it in the early 18th century. The freezing point of water is 0°Ré and the boiling point 80°Ré. This scale has been almost completely replaced by the Celsius scale.
Despite the Réaumur scale no longer being used, it had a significant impact in the history of temperature measurement.
About Rankine
Rankine is temperature unit normally used in thermodynamics. It is named after the Scottish engineer and physicist William John Macquorn Rankine, who is know for his work in thermodynamics. The Rankine scale is based on the Fahrenheit scale with degree increments identical but starting at absolute zero.
With the zero point at absolute zero (-459.67°F) it is easy to convert between Rankine and Fahrenheit: simply subtract 459.67.
The Rankine scale is not normally used in everyday life as it is an engineering unit particularly thermodynamics in the United States.