This is a Clilstore unit. You can link all words to dictionaries.

Basic Polygons



A polygon is a closed flat shape with straight edges. Closed means there are not gaps in the shape.

Each polygon is given a name, depending on how many sides it has. A 3-sided polygon is called a triangle; a 4-sided polygon is called a quadrilateral.

When a polygon has 5 or more sides, the names follow a simple pattern. A 5-sided polygon is called a pentagon; a 6-sided polygon is called a hexagon; a 7-sided polygon is called a heptagon; an 8-sided polygon is called an octagon; a 9-sided polygon is called a nonagon; a 10-sided polygon is called a decagon, and so on.

It’s important to learn the prefixes penta, hexa, hepta, octa, nona and deca as they appear in chemistry and many other English words.

When a polygon has a large number of sides, you can just call it an ‘n’-gon. A 20-sided polygon is a ‘20-gon’; a 39-sided polygon is a ’39-gon’, and so on.

Which of the following shapes are polygons?

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