Definition:Extension


 * In set theory:
 * Definition:Extension of Relation
 * Definition:Extension of Mapping
 * Definition:Extension of Operation
 * Definition:Extension of Sequence


 * In abstract algebra:
 * Definition:Field Extension
 * Definition:Ring Extension
 * Definition:Extension of Ideal
 * Definition:Extension of Scalars


 * In model theory:
 * Definition:Extension of Structure


 * In propositional logic:
 * Definition:Extension of Propositional Tableau


 * In physics:
 * Definition:Extension of Elastic Material

Warning
Do not confuse this with expansion, which is (among other things) a term used for a topology which is a superset of another topology.

Also see

 * Definition:Restriction