# Aggregation

### From Glossary

*Aggregation* is combining units
to reduce problem dimensions. One form of aggregation is to combine
basic entities at the data level, such as regions, time periods,
and materials. The dimensions of the mathematical program, which
include numbers of variables and constraints, are generally reduced
by aggregation at the entity level. Another form of aggregation is
the use of surrogates, including the strong form: integer equivalent aggregation.