What are regular and irregular shapes?

The definition of a regular shape is that all the sides are equal and all the inside angles are equal. An irregular shape doesn’t have equal sides or equal angles.

For example, an equilateral triangle is a regular shape because all the sides are equal AND all the angles are equal. A right angle triangle is an irregular shape, because although it is a shape that we recognise instantly, it has different length sides and different inside angle measurements.

What are regular shapes?

Regular means ordered or predictable. Children are taught the names of shapes (or polygons) from a very early age and usually shown the regular version of the shapes to help with easy recognition. Here are the most common ones:

What are regular and irregular shapes?

Remembering shape names

Some shape names are much easier to remember than others, most know what a circle and a square are, for example. Triangles are also fairly straightforward; however, the only regular triangle is equilateral. the clue here is in the name (equal).

A Pentagon takes its name from the Greek language; pente, meaning five and gonia, meaning angle. Children are often shown a picture of the famous Pentagon building in America to help them remember. Another technique might be to remind them that you hold your pen in your hand and you have five fingers.

Hexagons can be remembered in two ways. Just like the number six, they have an ‘x’ in their name. Plus, they have six sides.

Heptagons are a little trickier, again the name is Greek in origin, but we come across them less often so it can be a struggle to remember. A 50p coin is a Heptagon.

An Octagon has eight sides just like an octopus. There are also eight Octonauts in the CBeebies series, which many children love. You may be able to link the two names to help them remember?

What are irregular shapes?

Irregular means not even or balanced. Irregular shapes (or polygons) are often much harder for children to name because they don’t look like the more conventional regular shapes. In fact, they can be any straight-sided shape. Their name is often determined by the number of straight sides that they have, although some irregular polygons have special names like parallelograms, rhombus or kite. Here are some examples:

What are regular and irregular shapes?

Worksheets and Practice

Regular and irregular shapes are great fun! Here is a list of EdPlace worksheets that'ss help you get to grips with this topic. Why not give them a try?

Year 1 – Introducing shapes

Year 2 – Spot the 2D shapes on common 3d objects

Year 3 – Are the shapes 2D or 3D?

Year 4 – Name the triangle

Year 4 – Identify quadrilaterals

Year 5 – Regular and irregular polygons

Year 5 - Rectangle problems

Year 5 – Rectangle facts

Year 5 – Angle multiples of 90 degrees

Year 6 – Calculate areas: triangles

Year 6 – Calculate areas: Parallelograms

Further Information

If shapes are your thing and you really want to give yourself a challenge, why not look at the BBC Bitesize website or try some of the puzzles and problems set by the NRich team from The University of Cambridge?

https://nrich.maths.org/public/leg.php?code=120

https://nrich.maths.org/9021

http://www.bbc.co.uk/bitesize/ks2/maths/shape_space/2d_shapes/read/1/