Each [[Segmentum]] is divided into '''Sectors'''are divisions of [[segmentus|Segmenta]]. The size of a sector varies according to local demands and stellar density. A typical sector might encompass 7 million cubic light years, equivalent to a cube with sides almost 200 light years long. Sectors are in turn divided into ''subsectors''. '''Subsectors''' usually comprise between 2 and 8 star systems within a 10 light year radius (some may encompass more systems - others only 1). This size is governed by the practical patrol ranges of spaceships. Because, unlike sectors, subsectors are divisions of worlds (rather than volumes of space) there are vast numbers of [[SubsectorSystem|star systems]]swithin each sector which do not fall within a subsector. These are referred to as inter sectors - and are commonly known as wilderness zones, forbidden zones, empty space and frontier space. Inter-sectors may contain gas or dust nebulae, inaccessible areas, alien systems, unexplored systems, uninhabited systems and uninhabitable worlds.