空洞|くうどうkuudou[0]heiban (flat)

1. nouncavity; hollow; cave; cavern
2. no-adjectivehollow

• Synonym洞窟どうくつNeutralA deep cave in a cliff or rock, as in 「洞窟を探検する」; 空洞 is the broader term for any cavity inside an object.
• Synonym洞穴ほらあなNeutralA cave in a mountain or hillside; 空洞 leans toward hollow spaces inside objects.
• Related風穴かざあなNeutralAn air vent or a cave that blows cold air, as in 「風穴を開ける」; 空洞 leans toward internal cavities.
• Related岩屋いわやWrittenWritten/formal prose for a natural rock cave or a dwelling carved into rock; 空洞 is the more general word.
• Related虚ろうつろWrittenWritten/formal prose. Covers hollow spaces and, figuratively, vacant eyes or empty words; 空洞 leans toward physical cavities.
• Related穴ぼこあなぼこCasualColloquial. A hole or depression, such as a pothole in the road; 空洞 is a cavity inside something.
• Related岩窟がんくつWrittenWritten/formal prose for a rocky cave; 空洞 is the more general word.
• Related岩穴いわあなNeutralA hole or natural cave in rock; 空洞 leans toward hollow spaces inside objects.
• Antonym充実じゅうじつNeutralFullness or substance, as in 「充実した一日」; the antonym of empty, hollow 空洞.

Use 「空洞」 for a cavity inside an object or, figuratively, for emptiness as in 「空洞化」. For actual caves choose 「洞窟」 or 「洞穴」; for potholes, colloquial 「穴ぼこ」; for hollow eyes or vacant expressions, 「虚ろ」. 「岩窟」 and 「岩屋」 are written words for rock caves, 「岩穴」 a hole in rock, and 「風穴」 a vent or cold-air cave. The opposite of hollow 「空洞」 is 「充実」.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 中なかに穴あながあいて空間くうかんがあること。また、その空間くうかん。
2. ほらあな。
3. 肺結核はいけっかくなどにより体内たいないの組織そしきが液化えきかして空間くうかんが生しょうじること。