The SI unit of temperature is the Kelvin, which is a six-letter word. The Kelvin scale is an absolute temperature scale that was named after the British physicist and engineer William Thomson, 1st Baron Kelvin. It is the primary unit of temperature measurement in the International System of Units (SI). The Kelvin scale is based on the concept of absolute zero, which is the temperature at which all thermal motion ceases. The Kelvin scale is used in scientific research and in many industrial and technological applications.