(くう) (n) (1) empty air; sky; (2) {Buddh} shunya (emptiness, the lack of an immutable intrinsic nature within any phemomenon); (3) (abbr) (See 空軍) air force; (n,adj-na) (4) fruitlessness; meaninglessness; (5) (See 五大・1) void (one of the five elements) [EDICT]
(そら) (n) sky; the heavens; (P) [EDICT]
(kōng, ㄎㄨㄥ) air; sky; empty; free time; in vain [CE-DICT]
(kòng, ㄎㄨㄥˋ) emptied; leisure [CE-DICT]
洞
(うろ) (n) hollow; cavity; hole [EDICT]
(ほら) (n) cave; den; grotto; (P) [EDICT]
(dòng, ㄉㄨㄥˋ) cave; hole; zero (unambiguous spoken form when spelling out numbers) [CE-DICT]