The mapping in which two different members of the range are mapped to the same member of the domain.
A graph in which at least two ordered pairs have the same -coordinate and different -coordinates.
![\"\"](\"/userfiles/image/steps_images/step1.JPG\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=8da2268e35b6b6daab9c47f71c4c8bf4.png\")
-coordinate and different ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=b1f02a70f7489dd3b8742e9e1c94d6d0.png\")
-coordinates.