Fourth dimension

3D projection of a rotating tesseract

"The concept of a fourth dimension is one that is often described in considering its physical implications; that is, it is known that there are three dimensions: length (or depth), width, and height. The fourth dimension is orthogonal to the other three spatial dimensions.

The cardinal directions in the three known dimensions are called up/down (altitude), north/south (latitude), and east/west (longitude).

When speaking of the fourth dimension, an additional pair of terms is needed. Attested terms include ana/kata (sometimes called spissitude or spassitude), vinn/vout (used by Rudy Rucker), and upsilon/delta.

The fourth dimension is often identified with time, and as such is used to explain space-time in Einstein's theories of special relativity and general relativity. In this case, the concept of an additional spatial dimension would be referred to as the fifth dimension."

in Wikipedia.com