# 2-D Shapes

2-D shapes or two-dimensional shapes are flat. They can be described using lots of different mathematical vocabulary. See how many of the 2-D shapes below you recognise. Try to use the mathematical vocabulary to describe each of the shapes.

## Important Shape Vocabulary

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.

If you want to know more about shape angles make sure you read our Shape Angles Blog.

### Polygon

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

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:

• Circle
• Triangle
• Semi-circle
• Square
• Rectangle
• Parallelogram
• Rhombus
• Trapezium
• Kite
• Polygons

### Elliptical shape

An elliptical shape is an elongated circle that has been stretched into an oval. Not every oval is an ellipse.

## 2-D shape names and facts

You can download a 2-D shape guide and a 2-D shape properties poster for free to support your understanding of 2-D shapes.

Look below to learn all about the properties of 2-D shapes in more detail.

## Circle

How many of these circle facts do you know?

• A circle is a two-dimensional geometric shape.
• A circle has 1 side.
• A circle has one curved side.
• A circle has no vertices.
• The outside of a circle is called the circumference.
• All points on the circumference of a circle are the same distance from the centre of the circle. This distance is called the radius.
• A circle has an infinite number of lines of symmetry.

## Oval

How many of these oval facts do you know?

• An oval is a two-dimensional geometric shape.
• An oval has 1 side.
• An oval has one curved side.
• An oval has no vertices.
• An oval generally has a line of symmetry.
• Some ovals have two lines of symmetry.

## Semicircle

How many of these semicircle facts do you know?

• A semicircle is a two-dimensional shape that forms half of a circle.
• A semicircle has 2 sides.
• A semicircle has one curved side and one straight side.
• A semicircle has two vertices.
• A semicircle has one line of symmetry.

## Triangle

How many of these triangle facts do you know?

• A triangle is a two-dimensional geometric shape.
• A triangle has 3 sides.
• A triangle has three straight sides.
• A triangle has three vertices.
• A triangle is a polygon.
• The sum of all the angles of a triangle is 180º.

### Types of triangles

Not all triangles are the same. All triangles have three straight sides, three vertices and their angles all add up to 180º.

But how are triangles different? Let's find out...

#### Equilateral triangle

An equilateral triangle has three sides. All the sides are the same length. Each of the interior angles of an equilateral triangle measures 60º.

#### Scalene triangle

A scalene triangle has three sides. All the sides are different lengths. The interior angles of a scalene triangle are all different.

#### Isosceles triangle

An isosceles triangle has three sides. Two of the sides are the same length, these sides are called the legs. The other remaining side is called the base. The interior angles opposite to the two equal sides are both the same size.

#### Obtuse triangle

An obtuse triangle has three sides. One of the interior angles of an obtuse triangle measures more than 90º but less than 180º.

#### A right angled triangle

A right angled triangle has three sides. One of the interior angles of a right angled triangle measures 90º.

How many of these quadrilateral facts do you know?

• A quadrilateral is a two-dimensional geometric shape.
• A quadrilateral has 4 sides.
• A quadrilateral has four straight sides.
• A quadrilateral has four vertices.
• There are six special quadrilaterals: square, rectangle, parallelogram, rhombus, trapezium, and kite.
• A quadrilateral is a polygon.

### Types of quadrilaterals

#### Square

How many of these square facts do you know?

• A square is a two-dimensional geometric shape.
• A square has 4 sides.
• A square has four straight sides.
• A square’s sides are all the same length.
• A square’s opposite sides are parallel.
• A square has four vertices.
• A square’s vertices are all the same size. The vertices are all 90º.
• All squares are rectangles but not all rectangles are squares.
• The sum of all the angles of a square is 360º. 90º + 90º + 90º + 90º = 360º
• A square is a polygon.

#### Rectangle

How many of these rectangle facts do you know?

• A rectangle is a two-dimensional geometric shape.
• A rectangle has 4 sides.
• A rectangle has four straight sides.
• A rectangle has two sets of sides that are the same length.
• A rectangle’s opposite sides are parallel.
• A rectangle has four vertices.
• A rectangle’s vertices are all the same size. The vertices are all 90º.
• The sum of all the angles of a rectangle is 360º. 90º + 90º + 90º + 90º = 360º
• A rectangle is a polygon.

#### Kite

How many of these kite facts do you know?

• A kite is a two-dimensional geometric shape.
• A kite has 4 sides.
• A kite has four straight sides.
• A kite has two pairs of sides that are the same length.
• A kite has four vertices.
• A kite has one pair of equal angles.
• A kite is a polygon.

#### Rhombus

How many of these rhombus facts do you know?

• A rhombus is a two-dimensional geometric shape.
• A rhombus has 4 sides.
• A rhombus has four straight sides.
• A rhombus has two pairs of sides that are the same length.
• A rhombus’ opposite sides are parallel.
• A rhombus has four vertices.
• A rhombus has two pairs of equal angles.
• Lines drawn joining the opposite angles of a rhombus bisect each other at right angles.
• A rhombus is a polygon.

#### Parallelogram

How many of these parallelogram facts do you know?

• A parallelogram is a two-dimensional geometric shape.
• A parallelogram has 4 sides.
• A parallelogram has four straight sides.
• A parallelogram has two pairs of sides that are the same length.
• A parallelogram’s opposite sides are parallel.
• A parallelogram has four vertices.
• A parallelogram has two pairs of angles that are all the same size.
• Lines drawn joining the opposite angles of a parallelogram bisect each other.
• A parallelogram is a polygon.

#### Trapezium

How many of these trapezium facts do you know?

• A trapezium is a two-dimensional geometric shape.
• A trapezium has 4 sides.
• A trapezium has four straight sides.
• A trapezium has one pair of parallel sides.
• A trapezium has four vertices.
• A trapezium is a polygon.
• A trapezium is sometimes called a trapezoid.

## Pentagon

How many of these pentagon facts do you know?

• A pentagon is a two-dimensional geometric shape.
• A pentagon has 5 sides.
• A pentagon has five straight sides.
• A pentagon has five vertices.
• The word pentago comes from the ancient Greek words pente meaning five and agon meaning angle.
• A pentagon is a polygon.

## Hexagon

How many of these hexagon facts do you know?

• A hexagon is a two-dimensional geometric shape.
• A hexagon has 6 sides.
• A hexagon has six straight sides.
• A hexagon has six vertices.
• The word hexagon comes from the ancient Greek words héx meaning six and agon meaning angle.
• A hexagon is a polygon.

## Heptagon

How many of these heptagon facts do you know?

• A heptagon is a two-dimensional geometric shape.
• A heptagon has 7 sides.
• A heptagon has seven straight sides.
• A heptagon has seven vertices.
• A heptagon is also known as a septagon.
• The word heptagon comes from the ancient Greek words heptá meaning seven and agon meaning angle.
• The word septagon comes from the Latin word sept meaning seven and the ancient Greek word agon meaning angle.
• A heptagon is a polygon.

## Octagon

How many of these octagon facts do you know?

• An octagon is a two-dimensional geometric shape.
• An octagon has 8 sides.
• An octagon has eight straight sides.
• An octagon has eight vertices.
• The word octagon comes from the ancient Greek words okta meaning eight and agon meaning angle.
• An octagon is a polygon.

## Nonagon

How many of these nonagon facts do you know?

• A nonagon is a two-dimensional geometric shape.
• A nonagon has 9 sides.
• A nonagon has nine straight sides.
• A nonagon has nine vertices.
• A nonagon is also known as an enneagon.
• The word nonagon comes from the Latin words nonus meaning nine and the ancient Greek word agon meaning angle.
• The word enneagon comes from ancient Greek meaning nine corners.
• A nonagon is a polygon.

## Decagon

How many of these decagon facts do you know?

• A decagon is a two-dimensional geometric shape.
• A decagon has 10 sides.
• A decagon has ten straight sides.
• A decagon has ten vertices.
• The word decagon comes from the ancient Greek words déka meaning ten and the agon meaning angle.
• A decagon is a polygon.

## Hendecagon

How many of these hendecagon facts do you know?

• A hendecagon is a two-dimensional geometric shape.
• A hendecagon has 11 sides.
• A hendecagon has eleven straight sides.
• A hendecagon has eleven vertices.
• The word hendecagon comes from the ancient Greek words hendéka meaning eleven and the agon meaning angle.
• A hendecagon is a polygon.

## Dodecagon

How many of these dodecagon facts do you know?

• A dodecagon is a two-dimensional geometric shape.
• A dodecagon has 12 sides.
• A dodecagon has twelve straight sides.
• A dodecagon has twelve vertices.
• The word dodecagon comes from the English words dodeca meaning twelve and the gon meaning angles. The word dodeca comes from the Ancient Greek word dōdeka. The word gon comes from the Ancient Greek word gōnos
• A dodecagon is a polygon.

## Tridecagon

How many of these tridecagon facts do you know?

• A tridecagon is a two-dimensional geometric shape.
• A tridecagon has 13 sides.
• A tridecagon has thirteen straight sides.
• A tridecagon has thirteen vertices.
• A tridecagon is a polygon.

How many of these tetradecagon facts do you know?

• A tetradecagon is a two-dimensional geometric shape.
• A tetradecagon has 14 sides.
• A tetradecagon has fourteen straight sides.
• A tetradecagon has fourteen vertices.
• A tetradecagon is a polygon.

## When are 2-D shapes taught in the Maths National Curriculum?

2-D shapes are taught as part of the geometry strands of the maths curriculum. This strand is called geometry - properties of shapes

2-D shapes are first taught in year 1 when children:

In year 2 children are taught to:

In year 3 children will:

In year 4 children:

In year 6 children:

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