Mapping unit in astrography.
Average density: 30 to 40 worlds per
Subsectors are noted within a sector
by their position using the first sixteen letters of the alphabet
In addition, they are named and may be called by a variety of synonyms
for subsector, including province, cluster, or district. Imperial convention
is to assign numbers to districts (for example, District
268) which are under Imperial protection because they are pending
into the Imperium.