Zeroth Law of Thermodynamics
If two 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.
- The zeroth law 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 temperature.
- The zeroth law came to light long after the first and second laws of thermodynamics had been discovered and numbered. Because the concept of temperature is fundamental to those two laws, the law that establishes temperature as a valid concept should have the lowest number. Hence, it is called zeroth law.