Is states that the entropy of a system approaches a constant value as the temperature approaches absolute zero.
Formula:
S -S0 = Kb ln Ω
Where:
S = system's entropy
S0 = initial entropy
Kb= Boltzmann constant
Ω = total microstates that are consistent with the system's macroscopic configuration.
Example:
Vapors of water are gaseous forms of water at high temperatures. The molecules in the steam move randomly. So, it has high entropy.
If the vapors are set for cooling this steam to below 100 degrees Celsius IT will get transformed into water, where the movement of the molecules will be restricted resulting in a decrease in entropy.