Celsius (or degrees Celsius) is a scale to measure temperature and is derived from an SI unit with the symbol °C.
Celsius is named after Anders Celsius and is a scale derived directly from the Kelvin scale and was established in 1742. Otherwise known as the centigrade scale, it is recognised and used worldwide.
The Celsius scale is exactly 273.15 below the Kelvin scale which is the SI unit for temperature.
Water melts just below 0 °C and boils just below 100 °C (assuming normal conditions). The Celsius scale is also commonly used to measure the weather (or atmospheric temperature) and body temperature to diagnose fever. A typical comfortable day is anywhere from 10 °C - 30 °C and a healthy body temperature is anywhere between 36.1 °C and 37.2 °C.
Degrees Celcius is measured using a thermometre.
Rankine (or degrees Rankine) is a scale of temperature derived from an imperial unit and is denoted by the symbol °R.
Rankine is defined as a vector or shift from the Farenheit scale. Like the Kelvin (but 11 years later in 1859), it was also developed by a physicist from Glasgow University - namely William John Macquorn Rankine and was proposed to be used in engineering systems where heat computations are done in degrees Farenheit rather than Celsius.
Zero on both the Kelvin and Rankine scales is absolute zero (infinite cold - or the absolute absence of any thermal energy whatsoever).
The boiling point of water is 671.64102 °R. The freezing point of water is 491.67 °R.