洞

The Chinese character 洞 (dòng) for "cave" or "hole" is a pictophonetic character, combining a phonetic component 穴 (xué) and a semantic component 壬 (rén). The phonetic component 穴 represents a cave or a hole, while the semantic component 壬 originally depicted a person with outstretched arms and legs, suggesting the idea of "opening" or "extending". When combined, the character 洞 conveys the meaning of a natural or man-made cavity in the ground or a mountain. It can also be used metaphorically to refer to a hidden or secluded place, such as a secret chamber or a place of refuge. In addition to its literal meaning, 洞 is also used in various Chinese idioms and expressions. For example, 洞若观火 (dòng ruò guān huǒ) means "as clear as seeing fire through a hole", describing something that is extremely obvious or easily understood. Another idiom, 茅塞顿开 (máo sè dùn kāi), literally means "the茅塞 (茅草塞住的洞) is suddenly opened", and is used to describe a sudden moment of enlightenment or understanding.