third law of thermodynamics
From Glossary of Meteorology
The statement that every substance has a finite positive entropy, and the entropy of a crystalline substance is zero at the temperature of absolute zero.
Modern quantum theory has shown that the entropy of crystals at 0 K is not necessarily zero. If the crystal has any asymmetry, it may exist in more than one state; and there is, in addition, an entropy residue deriving from nuclear spin.
See thermodynamic probability.