洞 洞 dong4
cave; hole; zero (unambiguous spoken form when spelling out numbers)

strokes 9
radical
水
水
strokes after radical 6
凹洞 凹洞 ao1 dong4
cavity; pit

白洞 白洞 bai2 dong4
white hole (cosmology)

别有洞天 別有洞天 bie2 you3 dong4 tian1
place of charm and beauty; scenery of exceptional charm; completely different world

冰洞 冰洞 bing1 dong4
hole in ice; crevasse

柏克里克千佛洞 柏克里克千佛洞 bo2 ke4 li3 ke4 qian1 fo2 dong4
Paziklike thousand-Buddha grotto in the Turpan basin, Xinjiang

虫洞 蟲洞 chong2 dong4
worm-hole (in cosmology and science fiction)

穿洞 穿洞 chuan1 dong4
pierce

打洞 打洞 da3 dong4
to punch a hole; to drill a hole; to dig a hole; to burrow

大地洞 大地洞 da4 di4 dong4
cavern

大浦洞 大浦洞 da4 pu3 dong4
Taepodong, North Korean rocket series

大浦洞二 大浦洞二 da4 pu3 dong4 er4
Taepodong 2, North Korean rocket

大浦洞二号 大浦洞二號 da4 pu3 dong4 er4 hao4
Taepodong 2, North Korean rocket

地洞 地洞 di4 dong4
tunnel; cave; burrow; dugout

洞察 洞察 dong4 cha2
to see clearly

洞察力 洞察力 dong4 cha2 li4
insight

洞察一切 洞察一切 dong4 cha2 yi1 qie4
to see everything clearly

洞穿 洞穿 dong4 chuan1
to penetrate; to pierce; to see clearly; to have an insight into

洞房 洞房 dong4 fang2
secret inner room; bridal room

洞房花烛 洞房花燭 dong4 fang2 hua1 zhu2
bridal room and ornamented candles; wedding festivities (idiom)

洞房花烛夜 洞房花燭夜 dong4 fang2 hua1 zhu2 ye4
wedding night

洞府 洞府 dong4 fu3
cave dwelling; legendary abode of immortals

洞见 洞見 dong4 jian4
insight; to see clearly

洞鉴 洞鑒 dong4 jian4
to examine deeply; to inspect closely

洞开 洞開 dong4 kai1
to be wide open

洞孔 洞孔 dong4 kong3
hole

洞口 洞口 dong4 kou3
cave mouth; tunnel entrance

洞口 洞口 dong4 kou3
Dongkou county in Shaoyang 邵陽|邵阳, Hunan

洞口县 洞口縣 dong4 kou3 xian4
Dongkou county in Shaoyang 邵陽|邵阳, Hunan

洞窟 洞窟 dong4 ku1
a cave

洞若观火 洞若觀火 dong4 ruo4 guan1 huo3
clear as a flame (idiom); to see things absolutely clearly

洞天 洞天 dong4 tian1
paradise; heavenly or beautiful place; fairyland

洞庭湖 洞庭湖 dong4 ting2 hu2
Dongting Lake in northeast Hunan province

洞头 洞頭 dong4 tou2
Dontou county in Wenzhou 溫州|温州, Zhejiang

洞头县 洞頭縣 dong4 tou2 xian4
Dontou county in Wenzhou 溫州|温州, Zhejiang

洞悉 洞悉 dong4 xi1
to clearly understand

洞泄 洞泄 dong4 xie4
lienteric diarrhea (TCM)

洞穴 洞穴 dong4 xue2
cave; cavern

洞螈 洞螈 dong4 yuan2
olm (Proteus anguinus)

洞子 洞子 dong4 zi5
cave; pit; (coll.) greenhouse

耳洞 耳洞 er3 dong4
pierced ear

防空洞 防空洞 fang2 kong1 dong4
air-raid shelter

风洞 風洞 feng1 dong4
wind tunnel

狗咬吕洞宾，不识好人心 狗咬呂洞賓，不識好人心 gou3 yao3 lv3 dong4 bin1 - bu4 shi2 hao3 ren2 xin1
a dog biting Lü Dongbin (idiom); to ill reward a person's kindness

涵洞 涵洞 han2 dong4
culvert; covered drain

黑洞 黑洞 hei1 dong4
(astronomy) black hole

黑洞洞 黑洞洞 hei1 dong4 dong4
pitch-dark

洪洞 洪洞 hong2 tong2
Hongtong county in Linfen 臨汾|临汾, Shanxi

洪洞县 洪洞縣 hong2 tong2 xian4
Hongtong county in Linfen 臨汾|临汾, Shanxi

克孜尔千佛洞 克孜爾千佛洞 ke4 zi1 er3 qian1 fo2 dong4
Kezil thousand-Buddha grotto in Baicheng 拜城, Aksu 阿克蘇地區|阿克苏地区, Xinjiang

坑洞 坑洞 keng1 dong4
hole; pit; pothole

空洞 空洞 kong1 dong4
cavity; empty; vacuous

空洞无物 空洞無物 kong1 dong4 wu2 wu4
empty cave, nothing there (idiom); devoid of substance; nothing new to show

空空洞洞 空空洞洞 kong1 kong1 dong4 dong4
empty; hollow; lacking in substance

库木吐拉千佛洞 庫木吐拉千佛洞 ku4 mu4 tu3 la1 qian1 fo2 dong4
Kumutula thousand-Buddha grotto in Kuqa, Xinjiang

老鼠洞 老鼠洞 lao3 shu3 dong4
mouse hole

零日漏洞 零日漏洞 ling2 ri4 lou4 dong4
zero-day vulnerability (computing)

龙洞 龍洞 long2 dong4
cave; natural cavern (in limestone)

漏洞 漏洞 lou4 dong4
leak; hole; gap; loophole

漏洞百出 漏洞百出 lou4 dong4 bai3 chu1
lit. one hundred loopholes (idiom); full of mistakes (of speech or article)

吕洞宾 呂洞賓 lv3 dong4 bin1
Lü Dongbin (796-), Tang Dynasty scholar, one of the Eight Immortals 八仙

门洞 門洞 men2 dong4
passageway; archway

闹洞房 鬧洞房 nao4 dong4 fang2
disturbing the privacy of bridal room (Chinese custom where guests banter with and play pranks on the newlyweds)

破洞 破洞 po4 dong4
a hole

千佛洞 千佛洞 qian1 fo2 dong4
Buddhist grottos

龋洞 齲洞 qu3 dong4
hole due to dental caries

人字洞 人字洞 ren2 zi4 dong4
Renzidong palaeolithic archaeological site at Fanchang 繁昌, Anhui

溶洞 溶洞 rong2 dong4
karst cave

山洞 山洞 shan1 dong4
cavern; cave

石洞 石洞 shi2 dong4
cave; cavern

水帘洞 水簾洞 shui3 lian2 dong4
cave with a waterfall at its mouth

隧洞 隧洞 sui4 dong4
tunnel

挖洞 挖洞 wa1 dong4
to dig a hole

无底洞 無底洞 wu2 di3 dong4
bottomless pit

小洞不补大洞吃苦 小洞不補大洞吃苦 xiao3 dong4 bu4 bu3 da4 dong4 chi1 ku3
A small hole not plugged will make you suffer a big hole (idiom); a stitch in time saves nine

小洞不堵，大洞吃苦 小洞不堵，大洞吃苦 xiao3 dong4 bu4 du3 - da4 dong4 chi1 ku3
A small hole not plugged will make you suffer a big hole (idiom); A stitch in time saves nine.

小洞不堵，大洞难补 小洞不堵，大洞難補 xiao3 dong4 bu4 du3 - da4 dong4 nan2 bu3
If you don't plug the small hole, the big hole will be hard to repair (idiom); A stitch in time saves nine.

小洞不堵，大洞受苦 小洞不堵，大洞受苦 xiao3 dong4 bu4 du3 - da4 dong4 shou4 ku3
A small hole not plugged will make you suffer a big hole (idiom); A stitch in time saves nine.

小洞不堵沉大船 小洞不堵沉大船 xiao3 dong4 bu4 du3 chen2 da4 chuan2
A small hole not plugged will sink a great ship.

小岩洞 小岩洞 xiao3 yan2 dong4
grotto

窑洞 窯洞 yao2 dong4
yaodong (a kind of cave dwelling in the Loess Plateau in northwest China)

钥匙洞孔 鑰匙洞孔 yao4 shi5 dong4 kong3
keyhole

一杆进洞 一桿進洞 yi1 gan1 jin4 dong4
(golf) hole in one

一击入洞 一擊入洞 yi1 ji1 ru4 dong4
hole in one (golf)

引蛇出洞 引蛇出洞 yin3 she2 chu1 dong4
lit. to pull a snake from its hole; to expose a malefactor (idiom)

藏经洞 藏經洞 zang4 jing1 dong4
cave holding scripture depository, part of Mogao cave complex 莫高窟, Dunhuang 敦煌

张之洞 張之洞 zhang1 zhi1 dong4
Zhang Zhidong (1837-1909), prominent politician in late Qing

钻洞 鑽洞 zuan1 dong4
to bore