# Third law of thermodynamics

From Glossary of Meteorology

## third law of thermodynamics

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.