Boundary
Zone
noun
What shows the district and region and where they exist? That would be the boundary. It is what surrounds every district and region, showing where it exists.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
この区域の治安を良くする方法について、何か提案はありませんか？
Do you have any suggestions on how to improve public safety in this area?
自転車の放置禁止区域に自転車をとめてしまい、罰金で一万二千円を取られた。
I parked my bicycle in a prohibited area and was fined 12,000 yen.
日本政府は、その区域の正確な大気中の放射能濃度を公表しているのですか？
Will the Japanese government announce the exact zone in the atmosphere where the radioactivity is concentrated?