TOPIC 1 · GRADE 3 FOUNDATION

Points, Lines, Segments, Rays, and Angles

Build the precise language used to describe every later picture and shape.

MA.3.GR.1.1

BIG IDEA

A point marks an exact location. Lines, segments, and rays differ by how far they continue; two rays with one endpoint form an angle.

WHAT TO KNOW

A line continues forever in both directions; arrows show that it does not stop.
A segment has two endpoints. A ray has one endpoint and continues in one direction.
An angle has a vertex and two rays called sides. Its opening—not the side length—determines its size.

WATCH OUT

A longer-drawn ray does not make a larger angle. Only the amount of turn between the rays matters.

TRY IT

Switch among the four objects and notice what the dots and arrows tell you.

Choose the next topic from the lesson rail when you are ready.