Question

Can you define an endpoint of a plane

Answer 1

Yes. The endpoint of a plane can be defined.

Consider the example of a wall in the room. There are 3 planes. The x plane i.e. horizontal plane. The y plane i.e. vertical plane. The z plane which is the plane directed outwards from the wall.

These 3 plane meets at the start/end of a wall i.e at a corner. The corners of the room are the starting and the ending points of planes in this case.

Therefore, in this case we can define the corner as the endpoint of a plane. The coordinates of the corner or endpoint of plane can be calculated by measuring the dimensions of the room.

Such planes have finite spread. There are also planes which do not have any end and they spread indefinitely in all direction. The endpoints can only be defined for planes with finite spread not for the infinite planes.

Answer 2

A plane is a two dimensional flat surface.It has no thickness and  extends infinitely in two directions .A plane is named by three points in the plane that are not on the same line .For example of a wall in the room. By endpoint we mean two points that  does not extend past either of the points .A ray has one endpoint, and a line segment has two endpoints .Planes are flat' and continue on forever.They do not have any endpoints.