are mutually perpendicular line in space. (-axes)
-axes are called coordinate axes.
is called origin. The coordinate of is .
The planes containing the pairs of intersecting lines are called coordinate planes named respectively as -planes.
The -axes are respectively perpendicular to -planes. The system of axes thus obtained is known as rectangular or orthogonal system of coordinate axes.
are called the non-negative -axes and are non-positive -axes respectively.
The above system of coordinates is known as the Rectangular Cartesian Coordinate System, named after the French mathematician Rene Descartes (1596-1650).
The three coordinate planes, intersecting at origin divide the set of points not living on any of the coordinate planes into eight disjoint convex sets known as Octants.
A three dimensional space with , we can describe the eight octants as follows: