Subspace

In mathematics, if a set with certain properties is called a space, then a subset with the same properties is usually called a subspace. Of a metric space, or topological subspace in topology, any subset can be taken; however, a linear subspace (also called vector subspace) in linear algebra is a special subset.

There is a fictional notion of subspace used in science fiction; see Hyperspace (science fiction).

The psychological state of the submissive partner in a BDSM scene is sometimes described as "subspace" or "sub space": see subspace (BDSM)

Also another name for Hammerspace, commonly used in anime settings, referring to the ability of some characters, usually young females, to pull a mallet or other blunt object out of thin air, usually to hit a wayward boyfriend over the head.