| 1661 | A Guide To Remembering Japanese Characters (Kenneth G. Henshall) |
| 1756 | A New Dictionary of Kanji Usage |
| 2546 | Classic Nelson (Andrew Nelson) |
| 1468 | Japanese Kanji Flashcards (Max Hodges and Tomoko Okazaki) |
| 821 | Japanese Names (P.G. O’Neill) |
| 1301 | Kanji and Kana (Spahn and Hadamitzky) |
| 1380 | Kanji and Kana, 2nd Edition (Spahn and Hadamitzky) |
| 1844 | Kanji in Context (Nishiguchi and Kono) |
| 1191 | Kodansha Compact Kanji Guide |
| 455 | Kodansha Kanji Dictionary (Jack Halpern) |
| 280 | Kodansha Kanji Learner’s Dictionary (Jack Halpern) |
| 340 | Kodansha Kanji Learner’s Dictionary, 2nd Edition (Jack Halpern) |
| 183 | Les Kanjis dans la tete (Yves Maniette) |
| 17386 | Morohashi |
| 380 | New Japanese English Character Dictionary (Jack Halpern) |
| 3125 | New Nelson (John Haig) |
| 181 | Remembering The Kanji (James Heisig) |
| 193 | Remembering The Kanji, 6th edition (James Heisig) |
| 1276 | Tuttle Kanji Cards (Alexander Kask) |
Jōyō kanji, taught in junior high
JLPT level N1
1618 of 2500 most used kanji in newspapers
Stroke order
On reading compounds
- 洞 【ドウ】 sinus, cavity, antrum, neighborhood (administrative division in North Korea)
- 洞察 【ドウサツ】 discernment, insight
- 空洞 【クウドウ】 cavity, hollow, cave, cavern, hollow
- 風洞 【フウドウ】 wind tunnel
Kun reading compounds
- 洞 【ほら】 hollow, cavity, hole, cave
- 洞穴 【ほらあな】 cave, cavern, den, grotto
Readings
- Japanese names:
- とう
- Korean:
- dong, tong
Spanish
- cavidad
- hueco
- excavación
- prever
Portuguese
- gruta
- caverna
- escavação
French
- antre
- grotte
- excavation
| 349 | 2001 Kanji |
| 3a6.25 | The Kanji Dictionary |
| 1-3-6 | SKIP code |
| 3712.0 | Four corner code |
| 1-38-22 | JIS X 0208-1997 kuten code |
| 6d1e | Unicode hex code |
Stroke order
On reading compounds
- 窟院 【クツイン】 cave temple
- 巣窟 【ソウクツ】 den, haunt, hangout, nest, lair
- 宝窟 【ホウクツ】 treasure mine
Kun reading compounds
- 岩屋 【いわや】 cavern, grotto
Readings
- Korean:
- gul
Spanish
Portuguese
French
- grotte
- caverne
| 3331 | Classic Nelson (Andrew Nelson) |
| 1943 | Kanji and Kana, 2nd Edition (Spahn and Hadamitzky) |
| 2923 | Kodansha Kanji Dictionary (Jack Halpern) |
| 2032 | Kodansha Kanji Learner’s Dictionary, 2nd Edition (Jack Halpern) |
| 1335 | Les Kanjis dans la tete (Yves Maniette) |
| 25552 | Morohashi |
| 2328 | New Japanese English Character Dictionary (Jack Halpern) |
| 4206 | New Nelson (John Haig) |
| 2615 | Remembering The Kanji (James Heisig) |
| 1420 | Remembering The Kanji, 6th edition (James Heisig) |
| 3m10.6 | The Kanji Dictionary |
| 2-3-10 | SKIP code |
| 2-5-8 | SKIP code |
| 3027.2 | Four corner code |
| 1-23-02 | JIS X 0208-1997 kuten code |
| 7a9f | Unicode hex code |