Dimensions according to String Theory.

The official scientific definition of dimension is an axis for which things can exist on - for example, a point is 0 - dimensional, a line is 1 - dimensional, a plane is 2 - dimensional, a cube is 3 - dimensional, etc. Time is considered to be the fourth dimension. According to M theory their exist 11 spatial dimensions which are curled up into small objects which we can't interact with. This idea is very controversial in the physics community due to many reasons and isn't accepted yet.

In the OBD, the word "dimension" is more often used to designate a separate set of timespace, usually smaller than a universe, and can range from city-sized like in Pokemon to greater than multiple galaxies. This is also how it is used in many fictions. Destroying a dimension is considered to be a very impressive feat, although it depends a lot on the size and characteristics of the dimension. Contrary to typical DBZtard claims, creating a portal from one dimension to another is not a feat of power, simply a feat of transportation. Also, contrary to Bleachwanker claims, a power to use dimensions to BFR yourself does not necessarily imply the ability to BFR others.

Notable Dimensions:

Anti-Spiral Dimension, from TTGL
- Asgard, The Dark Dimension, Shuma's realm, Mephisto's realm, the Negative Zone (although it might qualify as a universe), the Quantum Zone, and many others from Marvel Comics
- Aslan's Country, Lantern Waste, and several others from The Chronicles of Narnia
Bionicle has many Pocket Dimensions (such as the realm of shadows) and many characters possess the ability to travel between them
- Blaze's dimension, Nameless zone, and Dimension bridge from Sonic the Hedgehog
- Configuration Space from Xeelee Sequence
- Realm of Space, Realm of Time, Reverse World, and Alternate Dimension from Pokemon
- Fold space from Macross
- Ghost Zone from Danny Phantom
- Heaven and Hell from the Preacher comics (Vertigo title)
- Heaven, Hell, and several others from Bastard!!
Hyperspace, from Star Wars
- Kalidoscopic Dimension (Dream Dimension), Dark Area, Data World, and Witchleny from Digimon
- Makai from Darkstalkers
- Magicus Mundus, Eva's resort and phantasmagoria realm, etc. from Negima
- Shadow Realms from Yu-Gi-Oh
- Soul Society and Hueco Mundo, from Bleach
- Subspace, from Scott Pilgrim
- Time, Hyperspace, Six-Fold-Realm (which includes the 6th-11th dimension), each individual TARDIS, and many others from Doctor Who
- The 4th World, The Phantom Zone, Neron's realm, The Speedforce, The 5th dimension, The Bleed, and many others from DC Comics
- The Dreamworld, N-field, and an unwound alternate dimension exist in Rozen Maiden
- The Earthrealm and other various realms from Mortal Kombat
The Room of Spirit and Time (Hyperbolic Time Chamber), Deadzone (non-canon), and Otherworld from Dragon Ball
- The Warp and various Necron dimensions from Warhammer 40,000

See also:

Dimensional Manipulation