sector of space; space sector
Used primarily in science fiction and space-related contexts to refer to a designated area or region of outer space.
敵艦隊が我々の宙域に侵入した。
The enemy fleet has entered our sector of space.
この宙域は航行禁止区域に指定されている。
This space sector has been designated a no-fly zone.
Compound of 宙 (ちゅう, 'space, mid-air') and 域 (いき, 'area, region'). The term is a modern coinage, likely influenced by science fiction terminology.