Explore · Mathematics · Geometry

Defining attributes of shapes

Distinguish defining attributes of shapes (e.g. triangles are closed and three-sided) from non-defining attributes (e.g. colour, orientation, overall size)

ages 6 to 78 practice questionsvideo included

What a learner can do afterwards

Build and draw shapes that possess defining attributes
Identify that a shape remains a triangle regardless of its size, colour, or orientation
Explain why a given shape is or is not a particular type based on its defining properties

1 · Read

Every triangle has 3 straight sides and 3 corners. That is what makes it a triangle. It does not matter what color it is, how big it is, or which way it is turned.

Turn this triangle, shrink it, or paint it purple. It still has 3 straight sides and 3 corners. Still a triangle.

Try it together

Mia draws a tiny green triangle on her paper. Then she draws a huge yellow triangle next to it. They look very different, but both have 3 straight sides that join up with no gaps, and 3 corners. So both are triangles.

To check if a shape is a triangle, do not look at the color or the size. Count the straight sides. If there are 3 sides and 3 corners, and the sides join up with no gaps, it is a triangle.

A triangle is a triangle because of its 3 sides and 3 corners, never because of its color, size, or direction.

2 · Watch

3 · Play

step 1 of 6

You have counted sides and corners before. On the playground there are shapes painted on the ground, and today the game is: only stand on the triangles. Mia finds a tiny green one, with a huge yellow one right next to it.

Mia is not sure the huge yellow one counts. What should she check?

Take it off screen

Print a worksheetA4 with an answer key page for grown-ups. No screen, no internet.

Where it sits

Learn first

2-D shapes 3-D shapes (age 5+)

This opens up

2-D shapes (age 6+)Drawing shapes with given attributes

Where this leads

Jobs that lean on this skill. Follow one to see everything it is built on.

Robotics Programmer Photographer Plumber Structural Engineer Welder Carpenter

Then practise

8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.

Spotted a problem on this page? Tell us