- SI unit of temperature, the absolute thermodynamic scale
- 0 K = absolute zero = -273.15 C, the lowest possible temperature
- increments equal to Celsius degrees: a change of 1 K = a change of 1 C
- defined since 2019 by fixing the Boltzmann constant at 1.380649e-23 J/K
- surface of the Sun: ~5778 K
- cosmic microwave background: 2.725 K
- room temperature: ~293 K
- named after Lord Kelvin (William Thomson)
- the scale where all thermodynamic equations work directly: PV = nRT uses kelvin