A cave is a large, natural hole or space in the ground or in the side of a mountain. It is usually formed over long periods of time by water or other natural forces.
From Old French 'cave', from Latin 'cava' or 'cavus' meaning 'hollow'. The idea focuses on an empty, hollowed-out space in rock or earth.
The same root that gives us 'cave' also hides in 'cavity' at the dentist—both are just hollows. Humans have used caves as homes, art galleries, and religious spaces, so this 'hole in rock' has been a kind of all-purpose room for thousands of years.
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