Editing Non-Euclidean geometry (section)

===Three-dimensional non-Euclidean geometry===
{{main|Thurston geometry}}
In three dimensions, there are eight models of geometries.<ref>* [[William Thurston]]. ''Three-dimensional geometry and topology. Vol. 1''. Edited by Silvio Levy. Princeton Mathematical Series, 35. Princeton University Press, Princeton, NJ, 1997. x+311&nbsp;pp. {{isbn|0-691-08304-5}} (in depth explanation of the eight geometries and the proof that there are only eight)
</ref> There are Euclidean, elliptic, and hyperbolic geometries, as in the two-dimensional case; mixed geometries that are partially Euclidean and partially hyperbolic or spherical; twisted versions of the mixed geometries; and one unusual geometry that is completely [[anisotropy|anisotropic]] (i.e. every direction behaves differently).