What are regular shapes?
A regular shape is a shape with equal angles and sides – its sides are all the same length, and its angles are all the same number of degrees.
What are irregular shapes?
On the other hand, an irregular shape has sides of different lengths and angles of various sizes. Irregular shapes are shapes where the sides and interior angles are different. As a result, they can be more challenging for children to identify, as they don’t look like the conventional shape they are used to seeing when they are initially introduced to shapes.
Distinguishing between regular and irregular shapes
When distinguishing between regular and irregular shapes, it’s essential to look at their sides and angles. Are the sides and angles the same or different?
For example, children will learn about equilateral triangles and isosceles triangles. An equilateral triangle, by definition, has all sides of an equal length and equal angles, which makes it a regular shape. However, if you look at the image below, the sides of an isosceles triangle aren’t all the same length, and its angles are also different. This means that an isosceles triangle is an irregular shape.
Is the term ‘shape’ the same as a ‘polygon’?
In short, the two terms don’t mean the same thing. But when children learn about shapes at school, they may also hear them referred to as regular and irregular polygons. A polygon is a 2D shape with straight sides, and the standard and irregular shapes, which children will learn about, are all 2D shapes with straight sides. That’s why, in this instance, the terms can be used interchangeably.
What are some examples of regular and irregular shapes?
The best way to learn about shapes is to look at examples! Pupils will be expected to know whether a shape is regular or irregular, so let’s look at some of the properties of these polygons.
Examples of Regular Shapes
The table below includes examples of regular polygons for helping children learn the names. When learning about different shapes in Maths, children must see a visual representation to help them remember the properties.
For example, an equilateral triangle has three sides and three equal angles, which can be seen in the picture. Here’s something handy: it’s called ‘equilateral,’ which can be associated with ‘equal.’ That’s easy to remember and associate the name with its properties!
A helpful way of teaching about shapes is to have children match the visual representations with the properties and names of the figures. We’ve included some valuable resources at the bottom of the page, but looking at the table below can also be a helpful way of familiarising children with different regular shapes.
Examples of Irregular Shapes
You can see some examples of irregular shapes in the table below. It’s possible to keep adding to the list by including irregular heptagons, irregular octagons, etc.
What’s important to remember for irregular polygons is that although they might have one or two equal sides or angles, they’re still irregular. Only shapes with all their sides of equal length and all equal angles are regular.
How to Distinguish between Regular and Irregular Shapes
Before categorizing shapes into regular and irregular, children should be familiar with important shape names and their properties. But when they need to decide whether a polygon is regular or irregular, here’s a quick guide to what to look for:
- If given just the name, try to visualize it. The terms can often give you some hints, too. For example, a right-angled triangle has a right angle, which means it cannot be a regular shape (an equilateral triangle’s angles are all 60°). So, it’s an irregular one.
- Once you’ve visualized it or if you’ve been given an image, have a close look at the sides and angles. Of course, if you remember the properties of the shape (for example, a rectangle has equal angles, but not all sides are equal), then you have your answer. But looking at the sides and angles can help if you’re unsure.
- First, answer the question in your mind: are all sides equal? Even if the polygon has two equal sides, if the others are of a different length, it’s an irregular form, and you’ve got your answer! But if all the sides seem to be equal, then have a look at the angles.
- Do the angles appear to be equal? If they are and you’ve checked that the sides are equal, it’s a regular shape. If the angles are different, then it’s an irregular polygon.
