The term 'temperature unit' refers to the various ways of measuring temperature. The most common units are DEGREE (6 letters), therm (5 letters), kelvin (6 letters), and BTU (3 letters). DEGREE is a unit of temperature measurement that is used in both the Celsius and Fahrenheit scales. Therm is a unit of energy measurement that is equal to 100, 000 British thermal units. Kelvin is a unit of temperature measurement that is based on the absolute zero point of temperature. Finally, BTU is a unit of energy measurement that is equal to the amount of energy required to raise the temperature of one pound of water by one DEGREE Fahrenheit.