Zeroth Law of Thermodynamics
If systems A and B are each in thermal equilibrium with a third system C, then A and B are in thermal equilibrium with each other.
(1) The zeroth jaw leads to the concept of temperature. All bodies in thermal equilibrium must have a common property which has the same value for all of them. This property is called the temperature.
(2) The zeroth law came to light long after the first and seconds laws of thermodynamics had been discovered and numbered. It is so named because it logically precedes the first and second laws of thermodynamics.