洞穴・ほら穴|ほらあなhoraana[0]heiban (flat)

1. nouncave; cavern; den; grotto
   その洞穴ほらあなはその少年しょうねんたちによって発見はっけんされたのですか。↗

   Was the cave found by the boys?

• Synonym岩屋いわやNeutralA cave formed in rock; can also mean a dwelling carved into rock. It stresses the rock more than 「洞穴」 does.
• Synonym洞窟どうくつNeutralThe most common everyday word; stresses a deep, extensive hollow and is the usual term for cave exploration and sightseeing.
• Synonym空洞くうどうNeutralA cavity or hollow space; also used figuratively for content that is empty, giving it a wider range than 「洞穴」.
• Synonym岩窟がんくつWrittenWritten/formal word for a cave in rock, also written 「巌窟」. More literary and old-fashioned than 「洞穴」, and rare in everyday use.
• Related岩穴いわあなNeutralA hole in rock. Rare, and it emphasizes the rock material more than 「洞穴」 does.
• Related岩室いわむろWrittenWritten and rare; a rock cave or stone chamber that stresses a room-like space.

For caves in cliffs and rock, 「洞窟」 and 「洞穴」 are the everyday choices. Rock caves can also be called 「岩屋」 or, in written prose, 「岩窟」. For a hollow or cavity, including figurative emptiness, use 「空洞」.

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

1. （どうけつ）洞窟どうくつ。