Trans Galactic Void
The space between galaxies is called TGV or Transgalactic Void.
It is space that is near star and object empty. It is not completley without stars, dark objects and micro matter, but there are vast areas with no more than than a fewhydrogen atoms per cubic light year
Since the Union makes use of Trans Galactic Void (Station String Connections aka "Transgalactic Bridges ". The TGV is also subject to mapping and survey.
A Trans Galactic Void is defined as a space of 10 x 10 x 10 million light years or 10 LY3, divided into TGV-Cubes of 1 million light years. (A TGV Cube is designated as LG-TGV and a number (example: LG-TGV 9-8-8)
Each LG-TGV is subdivided into 100,000 LY Cubes (example LG-TGV 9-8-8:10-05-08)