Farenheit (or degrees Farenheit) is a scale to measure temperature and is part of the imperial / US customary unit system with the symbol °F.
The Farenheit scale was proposed in 1724 by Daniel Gabriel Farenheit and was the first standardized temperature scale to be widely used.
0 °F was set as the freezing point of a solution made from equal parts ice, water and salt. It was then established that the melting point of ice was 32 °F and human body temperature was 96 °F (or 98.6 °F when the scale was redefined into the modern version of the scale).
It is still used in the US and some associated territories as the official temperature scale. Everywhere else in the world uses Celsius.
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.