Two-dimensional graph
（重定向自Graph of a relation）
![](/Images/godic/202501/16/Cubicpoly.svg2031.png")
![Circle of radius r = 1, centre (a, b) = (1.2, −0.5)](/Images/godic/202501/16/Circle_center_a_b_radius_r.svg2031.png")
![The price P of a product is determined by a balance between production at each price (supply S) and the desires of those with purchasing power at each price (demand D). The diagram shows a positive shift in demand from D1 to D2, resulting in an increase in price (P) and quantity sold (Q) of the product.](/Images/godic/202501/16/Supply-and-demand.svg2031.png")
![Geometric shapes in 2 dimensions](/Images/godic/202501/16/Area.svg2032.png")
A two-dimensional graph is a set of points in two-dimensional space. If the points are real and if Cartesian coordinates are used, each axis depicts the potential values of a particular real variable. Often the variable on the horizontal axis is called x and the one on the vertical axis is called y, in which case the horizontal and vertical axes are sometimes called the x axis and y axis respectively. With real variables on the axes, each point in the graph depicts the values of two real variables.