Geometry Basics • Topic 3 of 5

Rays

A ray is part of a line that has one endpoint and extends without end in one direction, shown with a single arrowhead. It is named by its endpoint first, then any other point it passes through. Rays are the sides of angles: two rays sharing a common endpoint form an angle, and that shared endpoint is the vertex. Understanding rays clarifies how angles are built and measured. A ray is “half” of a line in the sense that a point on a line splits it into two opposite rays. On the SAT, rays appear mostly as the sides of angles in diagrams.

Two rays from a common endpoint O forming an angleRays form an angleO

✅ Solved examples

1. How many endpoints does a ray have?
One.
2. Two rays sharing a common endpoint form what?
An angle.
3. What is the common endpoint of an angle’s two rays called?
The vertex.
4. A point on a line creates two of what, pointing opposite ways?
Two opposite rays.

✏️ Practice — try these, take hints as needed

1. A part of a line with one endpoint extending one way is a:
One endpoint.
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—
Ray.
2. Two rays from a common point form a:
Shared endpoint.
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—
An angle.
3. The shared endpoint of the rays forming an angle is the:
Corner of the angle.
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—
Vertex.
4. How many arrowheads does a ray have?
Extends one direction.
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—
One.
5. A ray is named starting with which point?
Endpoint comes first.
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—
Its endpoint.

📝 Topic test — 8 questions

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