洞 den, cave, excavation 9 strokes jōyō, taught in secondary school old JLPT 1 #1618 in newspapers Readings Onドウ Kunほら In Chinese 洞 Words written with it 空洞 くうどう cavity 洞 ほら hollow N1 洞察 どうさつ discernment 洞窟 どうくつ cave 洞穴 ほらあな cave 鍾乳洞 しょうにゅうどう limestone cave 風洞 ふうどう wind tunnel