A 2D shape is a flat shape. They are shapes that only have 'two-dimensions' which means that they only have length and width. This is in contrast to 3D (three-dimensional) shapes which also have height.
Before we look at examples of 2D shapes, let's begin by unpicking their properties. Knowing what the vocabulary means is really important for children when they come to describing the properties of 2D shapes.
The side of a 2-D shape is the line that forms the outline of the shape. Sides can be straight or curved. A line is another word for a side.
The corner of a 2-D shape is the point where two sides meet. A corner is also called a vertex, the plural of vertex is vertices.
A curved line is not straight. It bends.
A straight line does not have a bend or curve.
A horizontal line goes from left to right (or right to left) across a page. Horizontal lines are parallel to the horizon.
A vertical line goes from top to bottom (or bottom to top) of a page. Vertical lines are perpendicular to the horizon.
Parallel lines travel in the same direction and are always the same distance apart. They never meet.
Perpendicular lines intersect at a right angle.
The intersect is the point where two lines meet.
A regular 2-D shape’s sides and angles are all equal. For example, all the angles in a regular triangle equal 60º.
An irregular 2-D shape has sides and angles of differing sizes.
A polygon is a 2-D shape with straight sides. The sides must be straight and closed. Polygons can have any number of sides. Triangles and squares are polygons. A polygon with 10 sides is called a decagon. A polygon with 100 sides is called a hectogon. A polygon with 1000 sides is called a chiligon. A polygon with 1 billion sides is called a gigagon.
Geometric shapes are regular shapes. Most geometric shapes have straight lines, angles and points. The two exceptions to this rule are circles and semi-circles.
The ten basic geometric 2D shapes are:
An elliptical shape is an elongated circle that has been stretched into an oval. Not every oval is an ellipse.
1. Shape sorting - giving children a collection of 2D shapes and asking them to sort them by number of sides, vertices or type can be a really useful activity. Make sure to include a range of different versions of each shape so that children used to seeing both regular and irregular versions of the shapes. Also make sure to show 2D shapes in different orientations - just because the rectangle is 'slanted' doesn't mean it isn't still a rectangle!
2. Shape riddles - Children could be asked to identify a 2D shape from a description of its properties. Alternatively, they could write their own riddles for each other, trying to use the correct vocabulary. You could give children a word bank with the vocabulary you want them to include in their riddles.
3. Spot the Shape! Children could be asked to go on a shape hunt around the classroom or school. Perhaps provide them with a checklist or table in which to record the shapes they find.
4. Spot the difference - Show children 2 shapes on the board and ask them to state as many differences as they can between them. This is a really good way to get them to use the vocabulary associated with 2D shape so be sure to have a word bank visible for children to refer to.
5. Make it! Why not get your class to make 2D shapes from art straws. By physically making the shapes and talking about their properties, children are much more likely to remember them.
6. Take it outside! Children love being outside so why not set up a scavenger hunt type activity. You could print out images of 2D shapes and pin them up around the playground, numbering them. Then, children could see how many they can find, recording the name of each one they find on a sheet of paper e.g. 1 = triangle 2 = circle 3 = regular hexagon 4 = irregular octagon etc.
A circle is a 2D shape that has one curved side. Circles are completely round as each point on its curved side is an equal distance from the centre of the circle. Circles have no vertices.
A semi-circle is half of a circle. It therefore has two sides, one of which is curved and one which is straight.
A triangle is a 2D shape that has three straight sides and three vertices.
There are different types of triangle:
1. Equilateral triangles - triangles which have three sides of equal length and three equal angles. Each angle will be 60 degrees.
2. Isosceles triangles - triangles which have two sides of equal length and two angles the same size.
3. Scalene triangles - triangles with no sides of equal length and no angles that are the same size.
4. Right-angled triangles - Triangles that contain a right-angle.
Quadrilaterals are shapes which have four straight sides and four vertices.
There are many different types of quadrilateral:
1. Squares - A square has four sides of equal length and four right angles.
2. Rectangles - A rectangle has for sides and four right angles. Opposite sides of a rectangle are the same length, with one pair being longer than the other pair.
3. Kites - Kites have two pairs of sides. These pairs are of equal length and they are adjacent to each other. Where these two pairs meet, the angles are equal.
4. Parrallelogram - A parrallelogram has opposite sides that are both parrallel and equal in length. Opposite angles are also the same.
5. Trapezium - A trapezium is a type of quadrilateral that has one pair of opposite sides that are parrallel with one another.
Pentagons - Pentagons have five sides and five vertices.
Hexagons - Hexagons have six sides and six vertices.
Heptagons - Heptagons have seven sides and seven vertices.
Octagons - Octagons have eight sides and eight vertices.
Nonagons - Nonagons have nine sides and nine vertices.
Decagons - Decagons have ten sides and ten vertices.
Hendecagons - Hendecagon have eleven sides and eleven vertices.
Dodecagons - Dodecagons have tweleve sides and tweleve vertices.
Tridecagons - Tridecagons have thirteen sides and thirteen vertices.
Tetradecagons - Tetradecagon have fourteen sides and fourteen vertices.
Here is what the National Curriculum says about teaching geometry in Year 1:
Pupils should be taught to:
Here is what the National Curriculum says about teaching geometry in Year 2:
Pupils should be taught to:
Here is what the National Curriculum says about teaching geometry in Year 3:
Pupils should be taught to:
Here is what the National Curriculum says about teaching geometry in Year 4:
Pupils should be taught to:
Here is what the National Curriculum says about teaching geometry in Year 5:
Pupils should be taught to:
Here is what the National Curriculum says about teaching geometry in Year 6:
Pupils should be taught to:
