Points

A point is thought as a “dot” on a piece of paper. A point has no length, width, or height. It just specifies an exact location. It is zero-dimensional. The following is a diagram of points A, B, and M.

Lines

A line is one-dimensional. That is, a line has length, but no width or height. A line extends forever in both directions. A line is uniquely determined by two points.

The line passing through the points A and B is denoted by

Line Segment

A line segment connects two endpoints. A line segment with two endpoints A and B is denoted by .

A line segment can also be drawn as part of a line.

Mid-Point

The midpoint of a segment divides the segment into two segments of equal length. The diagram below shows the midpoint M of the line segment . Since M is the midpoint, we know that the lengths AM = MB.

Rays

A ray starts from one endpoint and extends forever in one direction.

A ray starting from point A and passing through B is denoted by. Planes are two-dimensional. A plane has length and width, but no height, and extends infinitely on all sides. Planes are thought of as flat surfaces, like a tabletop. A plane is made up of an infinite amount of lines. Two-dimensional figures are called plane figures.

Space

Space is the set of all points in the three dimensions – length, width, and height. It is made up of an infinite number of planes. Figures in space are called solids.