1. 구 (九) -- nine.
This is the Sino-Korean form of the pure-Korean word 아홉. It is preceded by the number 팔 and followed by 십.
See also: Counting in Korean
2. 구 (口) -- a suffix meaning entrance, hole, wicket.
- 접수구 a reception counter
- 출납구 a teller's window
3. 구 (區) -- a ward or district (in a city); a territory or area.
See also: Gu, 구역