A flat shape with straight sides is named by how many sides it has. Touch each side once as you count round, and stop when you get back to the side you started on. 3 sides make a triangle, 5 a pentagon and 6 a hexagon. A shape with 4 sides and square corners is a square if every side is the same length, and a rectangle if two sides are longer. A circle has one curved edge and no corners. Turning, stretching or denting a shape does not change its name: a triangle is still a triangle when it points down, and an L-shape with 6 sides is a hexagon.
Explore this idea with maths tools
Maths you can move
Build 8 + 5
Tap two gold counters to fill the ten-frame.
8 in the frame + 5 waiting. The total stays the same.
Words to know
- side
- a straight edge of a flat shape
- corner
- where two sides meet (also called a vertex)
- hexagon
- any flat shape with 6 straight sides
Worked examples
A shape has 3 straight sides. What is its name?
- 1.Count the sides: 1, 2, 3.
- 2.3 sides make a triangle.
= triangle
A square is turned so it stands on one corner. What is its name now?
- 1.It still has 4 equal sides and 4 square corners.
- 2.Turning does not change the name.
= square
An L-shaped outline has 6 straight sides. What is its name?
- 1.Count every side, even round the inside corner: 1, 2, 3, 4, 5, 6.
- 2.6 sides make a hexagon.
= hexagon
For parents
Method: Count the sides, touching each one once.
What to say: Put your finger on one side. Count round until you get back to it. How many sides? What do we call a shape with that many sides?
Common mistakes:
- Counts the side they started on again at the end, so the count is one too many and the shape gets the next name up.
- Loses track while counting round the outline and misses a side, giving the name for one side fewer.
- Uses 'square' for every four-sided shape, so a rectangle is called a square.
- Thinks a square turned onto its corner becomes a different shape and calls it a 'diamond'.
- Uses the name of a solid for a flat shape: a circle is called a sphere, a square a cube, a triangle a pyramid.
- Knows the shape has many sides but attaches the wrong polygon name (pentagon for a hexagon's name, hexagon for an octagon's).