Euclidean space

https://en.wikipedia.org/wiki/Euclidean_space

Euclidean space is the fundamental space of geometry. Originally, this was the 3D space of Euclidean geometry, but, in modern mathematics, there are Euclidean spaces of any nonnegative integer dimension, including the 3D space and the 2D Euclidean plane. The qualifier "Euclidean" has been added when other kinds of spaces were discovered.

After the introduction at the end of 19th century of non-Euclidean geometries, the old postulates have been formalized for defining Euclidean spaces through an axiomatic theory.