A cavern is a large cave or a large chamber in a cave. Or, if your bedroom is very dark, your mother might want you to open the blinds and let some light into that cavern.
The word cavern is a late Middle English word that comes from the Latin root cavus, meaning “hollow.” Cavern typically describes a cave, but it can refer to any large enclosed space, especially a space that's dark like a cave. You might sit in a vast cavern when you go to the opera. Cavern can also be used figuratively — you could explore the dark cavern of your mind.
