Points, Lines, Line Segments, Rays, and Angles
1) Points
A point is an exact location or position. It has no length, area, or volume, but we usually draw it as a little dot to show where it is on a surface.
The three points on the right (labeled A, B, and C) are located inside the rectangle.
2) Lines
A line is straight and continues in both directions forever. Because lines are infinitely long, we can only draw a small part of them so that they don’t run off of the page! We must put arrowheads at each end of our line drawings, which tell us that the lines extend forever in the direction they are pointing to.
Be careful. Although we drew the left line a lot shorter than the right line, they still both continue forever in both directions (the right line is not “longer” than the left line in math).
3) Line Segments
A line segment is a small piece of a line. Unlike lines, line segments do not go on forever. We can draw line segments by connecting two points in a straight path. Line segments CAN be longer or shorter than one another depending on how you draw them, since they don’t go on forever.
The two points at the ends of line segments are called endpoints. Make sure to clearly draw the two endpoints as dots. There is no such thing as a line segment without endpoints!
4) Rays
A ray is part of a line with one endpoint. It starts at the endpoint and continues in one direction without ending. It is drawn with an endpoint at one end and an arrowhead at the other.
Sunlight is like a “ray” because it starts at one point (the sun) and the light shoots off in one direction forever.
5) Angles
An angle is formed when two rays share an endpoint. This shared endpoint is called a vertex.
The hands on a clock always make an angle. In this example, the vertex would be the center of the clock, where the two hands are connected.