Rays, Lines, and Angles

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Point
A Point is used to represent a single location in space.

Figure 1.

Above, we have a single point in space.

Ray
A Ray is a line that starts at a point and extends infinitely in one direction.

Figure 2.

Now, we've turned our Point into a Ray. This is Ray AB, because it extends from Point A to Point B.

Line
A line connects two points and extends infinitely in two directions.

Figure 3.

Now, we've turned our Ray into Line AB.

Angle
An angle is formed by two rays with the same endpoint.

Figure 4.

Here, we've connected two Rays to form an Angle. We can call it either angle CAB (or BAC), or angle 1.

Angles are measured using degrees, as shown below. We'll spend more time talking about angles in future lectures.

Figure 5.