# Polyhedron

### From Glossary

(pl. *polyhedra*). A set that equals the intersection of a finite number of halfspaces. This is generally written as
where the *representation* is not unique. It is often useful to separate the implied equalities:
so that the relative interior is
The system,
is a *prime representation* if it is irredundant, and it is *minimal* if it is irredundant and contains no implied equality. A polyhedron is degenerate if it contains an extreme point that is the intersection of more than halfspaces (where is the dimension of the polyhedron). An example is the pyramid.