The kanji 洞 means "cave," "den," "hole," or "cavity." It refers to an opening or hollow space, often natural, in the ground, rock, or other structures. It suggests a place that is enclosed and often dark.

・On-yomi (音読み): ドウ (dō) ・Kun-yomi (訓読み): ほら (hora)

⚫︎洞窟 Translation: cave ⚫︎空洞 Translation: cavity; hollow; empty space ⚫︎岩洞 Translation: rock cave

The kanji 洞 is a phono-semantic compound (形声文字, けいせいいもじ). ⚫︎The left side is the radical 氵 (water, みず), indicating something related to water or a wet environment. ⚫︎The right side is 同 (same, おなじ), which provides the sound and hints at the idea of something being connected or similar inside. ⚫︎Therefore, the character suggests a place such as a cave, often found near water.