Editing Subadditivity (section)

===Entropy===

[[Entropy]] plays a fundamental role in [[information theory]] and [[statistical physics]], as well as in [[quantum mechanics]] in a generalized formulation due to [[von Neumann entropy|von Neumann]].
Entropy appears always as a subadditive quantity in all of its formulations, meaning the entropy of a supersystem or a set union of random variables is always less or equal than the sum of the entropies of its individual components.
Additionally, entropy in physics satisfies several more strict inequalities such as the Strong Subadditivity of Entropy in classical statistical mechanics and its [[Strong subadditivity of quantum entropy|quantum analog]].