Noun
three-space (plural three-spaces)
(mathematics) A vector space whose basis of real numbers has three vectors
Stereographic projection of a 3-sphere (again removing the north pole) maps to three-space in the same manner. Source: Internet
When the system is used for physical three-space, it is customary to use positive sign for azimuth angles that are measured in the counter-clockwise sense from the reference direction on the reference plane, as seen from the zenith side of the plane. Source: Internet