• 区役所くやくしょ — ward office
• 地区ちく — local area, district
• 区分くぶん — classification, division
• 区画くかく — block, lot, section
• 学区がっく — school district
• 市区町村しくちょうそん — city, ward, town, and village (municipalities)

区 is derived from components meaning “to enclose” and “many items,” expressing the idea of separating or dividing space. It's used to denote sections within cities or organizations.

東京とうきょうには 二十三区にじゅうさんくがあります。
Tokyo has 23 wards.

この土地とちは 五ごつの区画くかくに 分わけられています。
This land is divided into five sections.