Several parts combine into one character.

The traditional 區 is a compound ideograph: 匚 (an open box / container) enclosing 品 (vessels / goods stacked together). The composite reads as "things separated and arranged within a container" = a divided area, district, ward. Both Japan (shinjitai) and Mainland China (simplified) reduced the inner 品 to a simpler X-like mark, producing 区. Korea retains 區.

Korean reading "gu." 區域 (guyeok, area / zone), 區別 (gubyeol, distinction / discrimination — making distinctions between things), 特區 (teukgu, "special zone" — used for special economic zones), 選擧區 (seongeogu, electoral district), 區廳 (gucheong, district office). Korean cities are subdivided into 區 (administrative wards): Seoul has 25 wards including Gangnam-gu, Jongno-gu, Yeongdeungpo-gu, and so on. Korean addresses follow a gu / dong / beonji (ward / neighborhood / lot-number) hierarchy.

Mandarin qū, 1st tone (simplified 区). 区 (qū), 区域 (qūyù, area), 区别 (qūbié, distinction), 地区 (dìqū, region), 特区 (tèqū, special zone — used for 经济特区 jīngjì tèqū "Special Economic Zone," like Shenzhen, Zhuhai, etc., the 1980s reform-era economic experiments), 开发区 (kāifāqū, development zone), 居民区 (jūmínqū, residential district). 区 is essential vocabulary in Chinese geography and economic policy.

Japanese on-reading ク (ku) — 区 (ku, ward), 区域 (kuiki, zone), 区別 (kubetsu, distinction), 区役所 (kuyakusho, "ward office" = district government office, where Japanese citizens register addresses and receive services), 特別区 (tokubetsu-ku, "special ward"). Tokyo is famously organized into 23 特別区 (tokubetsu-ku) — the 23 special wards of central Tokyo (Shinjuku-ku, Shibuya-ku, Setagaya-ku, etc.) which together form the core of the Tokyo metropolitan area. Each ku has its own ward office and elected mayor.

Memory aid: a container (匚) holding distinct things (品 → X) — divided space = ward / district. Korea uses 區, Japan and Mainland China use 区.