The Cartesian product of two sets 
and 
(also called the product set, set direct product, or cross
product) is defined to be the set of all points 
where 
and 
. It is denoted 
, and is called the Cartesian product since it originated
in Descartes' formulation of analytic geometry. In the Cartesian view, points in
the plane are specified by their vertical and horizontal coordinates, with points
on a line being specified by just one coordinate. The main examples of direct products
are Euclidean three-space (
, where 
are the real numbers), and
the plane (
).
The graph product is sometimes called the Cartesian product (Vizing 1963, Clark and Suen 2000).
