# Optimality gap

### From Glossary

Generally the difference between a best known solution, e.g. the incumbent solution
in mixed integer programming, and a value that bounds the best possible solution.
One such measure is the duality gap. The term is often qualified as the absolute gap, which
is the magnitude of the difference between the best known solution and the best bound, or as the relative gap, which
is the absolute gap divided by the best bound.