Complex sentence: From the modern viewpoint, there is essentially only one Euclidean space of ea is the Cartesian plane; and in higher dimensions it is a coordinate space with three or more real number coordinates.
Split into simpler sentences: From the modern viewpoint, there is essentially only one Euclidean space of each dimension. In dimension one this is the real line; in dimension two it is the Cartesian plane; and in higher dimensions it is a coordinate space with three or more real number coordinates.