compactification

Short definition from Wiktionary

Noun

1. 1
   Any of various procedures of enlarging a topological space to make it compact.
2. 2
   The space resulting from any such procedure.
3. 3
   Any modification of a theory such that an infinite parameter becomes finite.
4. 4
   The reduction of the number of large spacetime dimensions of a physical theory by making some of them compact.