Cavechat.org

On my trip to Ohio Caverns, I heard an interesting comment from the guide. She said that a cave is a natural passage underground with an opening to the surface, whereas a cavern is an underground passage closed off from the surface, which has to be artificially opened.
Is that an official definition?

I've always understood the cavern zone as the overhead environment where natural light reaches, once you go beyond the penetration of natural light you are in cave. I'm interested to hear what others have to say on this.

I've heard a dozen various definitions, all more or less arbitrary. I don't think there is an official distinction.

Officially, the difference between a cave and a cavern is about $20. "Cavern" sounds a whole lot more enticing than "cave," and this makes it easier for tourists to part with their money.

Cavern usually refers to the type of cave containing a large chamber or series of chambers/rooms. Not necessarily one which is dug open, nor one which natural light reaches.

I've never heard anyone claim it is about openings to the surface. The difference between a cave and a cavern is a matter of size, cavern connoting a large cave. Webster defines cavern as "an underground chamber often of large or indefinite extent."
A cave, on the other hand, simply is a "natural underground chamber or series of chambers."
Note that cavers (cave surveyors, mainly) have imposed different definitions on what a cave is for purposes of record keeping. In some states - Ohio - a cave is any natural opening large enough for a human to enter. In other areas, it requires at least 50 feet of passage to be listed. And yet others require a zone of darkness.
No matter the size of the cave or cavern, they still are pretty cool places.