Kelvin - Absolute temperature scale related to the Celsius (or Centigrade) relative scale. The Kelvin unit is equal to 1 C°; 0 Kelvin = -273.16°C; the degree sign and the word “degrees” are not used in describing Kelvin temperatures.

Kirchoff’s Law - In thermal equilibrium the absorbtivity of an opaque surface equals its emissivity (a = e).