The degree Celsius is a unit of temperature on the Celsius scale, a temperature scale originally known as the centigrade scale.
Fahrenheit is a temperature scale that bases the boiling point of water at 212 and the freezing point at 32.
The kelvin is a base SI unit of measurement, defined as the fraction 1/273.16 of the temperature of the triple point of water, which is the temperature at which water in solid, liquid, and gaseous state coexist in equilibrium.