Example: "z"("x","y")=2 is the constant function from "A"=ℝ² to "B"=ℝ where every point ("x","y")∈ℝ² is mapped to the value "z"=2. The graph of this constant function is the horizontal plane (parallel to the "x"0"y" plane) in 3-dimensional space that passes through the point (0,0,2).