Answer
A half-plane is a planar region containing all points on an infinite straight line on one side and no points on the other side.
Work Step by Step
Points can fall along the line, over the line, and beneath the line.
A half-plane is the arrangement of all above mentioned points on only one side of a line -- that is, either above or underneath the line.
If the coordinates on the line are considered, then it is called a closed half-plane. If the coordinates on the line are not considered, then it is called an open half-plane.
