...or are they their own mini "planes"? That is, can a creature teleport into our of of an extradimensional space or would plane shift be necessary to traverse its boundaries? Can divination spells detect creatures or objects through the extradimenional space's boundaries? And how about if the extradimensional space has been somehow rendered inaccessible (say by entering an antimagic field); where does the extradimenional space, and everything currently inside it, go?
Extradimensional spaces, by their very nature, are not of the same plane. The prefix "extra" means "outside of."
Intradimensional spaces, however, ARE of the same plane. The prefix "intra" means "inside of."
Take intragalactic (in our galaxy) and extragalactic (outside our galaxy), for example.
Non-dimensional spaces are spaces whose insides are typically larger than their outside. They too are NOT separate planes in their own right (at least as far as I can tell) and exist on the material plane just as an empty bag or house might.
From page 501 of Core:
Extradimensional Spaces
A number of spells and magic items utilize extradimensional
spaces, such as rope trick, a bag of holding, a handy haversack,
and a portable hole. These spells and magic items create a tiny
pocket space that does not exist in any dimension. Such items
do not function, however, inside another extradimensional
space. If placed inside such a space, they cease to function
until removed from the extradimensional space. For example,
if a bag of holding is brought into a rope trick, the contents of
the bag of holding become inaccessible until the bag of holding
is taken outside the rope trick. The only exception to this is
when a bag of holding and a portable hole interact, forming a
rift to the Astral Plane, as noted in their descriptions.
Take as you will.
Intradimensional spaces, however, ARE of the same plane. The prefix "intra" means "inside of."
I can't recall having ever seen the term "intradimensional" in a game book. Can you point me to one?
Non-dimensional spaces are spaces whose insides are typically larger than their outside. They too are NOT separate planes in their own right (at least as far as I can tell) and exist on the material plane just as an empty bag or house might.
Both the Bag of Holding and Portable Hole's descriptions refers to the space inside of them as "non-dimensional" whereas the rules on extradimensional spaces, as pointed out by Bruunwald, explicitly refer to both (along with the handy haversack and rope trick spell) as examples of "extradimensional" spaces. So it would seem that "non-dimensional" and "extradimensional" are synonymous terms.
So... my question remains: are such spaces, regardless of what they're called, part of the material plane or somehow apart from it?
I can't recall having ever seen the term "intradimensional" in a game book. Can you point me to one?There aren't any I can think of. He's just talking about the English language definitions.
So... my question remains: are such spaces, regardless of what they're called, part of the material plane or somehow apart from it?
For things like divination and teleportation and such, I believe the RAW is silent. Thus, it's a DM call. However, I suggest that, if the RAW is silent, turn to IRL. For example, the RAW is silent on whether you fall prone when you're knocked out, on how many toes a human being has, and so on, so we use IRL to fill those gaps. That said, "extradimensional", as Raving Dork said, has etymology which demands that it be outside the referred-to dimension. Thus, to answer your thread title, no; extradimensional spaces are not part of the material plane. Heck, I'd posit that they're not part of any plane but their own, because they're still "extradimensional" on the abyss, in heaven, on the plane of fire and so on.