This is the 9010th most frequent Japanese word.
洞
"洞" means "cave" or "hole" in English.
Here, '洞' (dou) in '洞窟' means 'cave,' referring to a hollow or cavern in the ground or rock.
洞窟にはたくさんのコウモリが住んでいます。
Many bats live in the cave.
In this example, '洞' (dou) is part of '洞察' which means 'insight' or 'deep perception,' emphasizing an ability to observe and understand deeply.
彼は問題を洞察する能力がある。
He has the ability to perceive issues deeply.
Here, '洞' (dou) combines with '影' (shadow) in '洞影,' depicting a deep or profound shadow/reflection, often poetic or aesthetic.