2D Shapes
A 2D (twodimensional) shape is a flat shape that has only two dimensions – length and width, with no thickness or depth. For example, a sheet of paper is twodimensional in shape. It consists of a length and a width but does not have any depth or height. Some common 2D shapes are square, rectangle, triangle, circle, and hexagon. In comparison to these, a 3D (threedimensional) shape has three dimensions – length, width, and height. For example, a dice is threedimensional because it consists of a length, a width, and a height. Some common 3D shapes are cuboid, cone, pyramid, and cylinder. Let us learn more about 2D shapes in this article.
1.  2D Shapes Definition 
2.  Regular and Irregular 2D Shapes 
3.  Difference Between 2D Shapes and 3D Shapes 
4.  Properties of 2D Shapes 
5.  Area and Perimeter of 2D Shapes 
6.  FAQs on 2D Shapes 
2D Shapes Definition
In geometry, 2D shapes can be defined as plane figures that are completely flat and have only two dimensions – length and width. They do not have any thickness and can be measured only by the two dimensions. A polygon is a 2Dimensional shape made up of straightline segments which are connected with each other, thus giving it a closed shape. A circle, square, rectangle, and triangle are some examples of twodimensional objects and these shapes can be drawn on paper. All the 2D shapes have sides, vertices (corners), and internal angles, except for the circle, which is a curved figure. 2D Shapes with at least three straight sides are called polygons and that includes triangles, squares, and quadrilaterals. The figure given below shows the 2D shapes that we commonly come across.
Regular and Irregular 2D Shapes
A 2D shape can be classified as regular or irregular based on the length and the interior angles:
 A 2D shape is said to be regular if all its sides are equal in length and all its interior angles measure the same.
 A 2D shape is irregular if all the sides are of unequal length and all its angles are of unequal measures.
Observe the following figure which shows the difference between regular and irregular 2D shapes.
Difference Between 2D Shapes and 3D Shapes
The following table shows a comparison between 2D and 3D shapes.
2D Shapes  3D Shapes  

FullForm  2DTwoDimensional  3DThreeDimensional 
Definition  2D shapes are flat and have only two dimensions of length and width with no thickness or depth.  A 3D shape has 3 dimensions of length,width, and height. 
Dimensions  Length and width only  Length, width and height 
Mathematical axes  xaxis and yaxis  xaxis, yaxis and zaxis 
Examples  Rectangle, square, circle, triangle, etc.  Cylinder, sphere, cube, prism, etc. 
Properties of 2D Shapes
2D shapes are flat and can be drawn on a sheet of paper. There are different types of regular and irregular 2D shapes like a circle, triangle, square, rectangle, pentagon, quadrilateral, and hexagon. Let us study each of them in detail, along with their properties.
Circle:
A circle is a closed 2D shape made up of a curved line with no corners or edges. Some reallife examples of the circle are coins, wheels, and pizzas. A circle consists of various parts like the radius, diameter, circumference, and so on.
Properties
Observe the properties of a circle to identify it as a 2D shape.
 Circles are completely round and made up of a single curved line.
 The circumference is the length of the boundary of the circle.
 The radius is the distance from the center of the circle to the boundary of the circle.
 The diameter is a line segment that goes straight across the circle, through the center. It is the longest possible line that can be drawn inside a circle and is twice the length of the radius.
Observe the following figure to see the different parts of a circle.
Triangle:
A triangle is a 2D shape with three sides and three vertices (corners).
Properties
Observe the properties of a triangle to identify it as a 2D shape.
 A triangle is a closed shape with 3 sides, 3 vertices and 3 angles.
 It is a polygon whose interior angles add up to 180°.
Some reallife examples of a triangle are traffic signs, pyramids, and nachos. The following figure shows the sides and vertices of a triangle.
Square:
A square is a 2D shape with four equal sides and each angle is equal to 90˚. Some of the reallife examples of a square are: a loaf of bread and a chessboard.
Properties
Observe the properties of the given square PQSR to identify it as a 2D shape.
 All four sides are equal, i.e., side PQ = QS = RS = PR
 Side PQ is parallel to RS.
 Side PR is parallel to QS.
 All four internal angles measure 90 ̊.
Rectangle:
A rectangle is a 2D shape with four sides in which the opposite sides are equal and parallel, and all the four angles measure 90 ̊. Some of the reallife examples of a rectangle are table tops, blackboard, cardboard, etc.
Properties
Observe the properties of the given rectangle ABCD to identify it as a 2D shape.
 Side AB = DC
 Side AD = BC
 Side AB is parallel to DC.
 Side AD is parallel to BC.
 All four angles measure 90 ̊.
Pentagon:
Pentagon is a 2D closed polygon with five sides and five interior angles. Some of the reallife examples of a pentagon are the black sections on soccer balls, school crossing signs, the Pentagon building in the US, etc.
Properties
Observe the properties of the given pentagon to identify it as a 2D shape.
 All five sides are equal in length.
 Each interior angle measures 108°.
 Each exterior angle measures 72°.
Hexagon:
A hexagon can be defined as a 2D polygon with six sides, six vertices and six angles. Some of the reallife examples of a hexagon are the honeycomb cells and metal nuts.
Properties
Observe the given regular hexagon and note the following properties to identify it as a 2D shape.
 All six sides are equal in length.
 Each interior angle measures 120°.
 Each exterior angle measures 60°.
Area and Perimeter of 2D Shapes
The area of a 2D shape is the size of the region enclosed within it. The perimeter of a 2D shape is the sum of the length of all the sides. The following table shows the formulas that are used to calculate the area and perimeter of a few common 2D shapes:
2D Shape  Area Formula  Perimeter Formula 

Circle  A = π × r^{2} where 'r' is the radius of the circle and 'π' is a constant whose value is taken as 22/7 or 3.14  Circumference (Perimeter) = 2πr 
Triangle  Area = ½ (Base × height)  Perimeter = Sum of the three sides 
Square  Area = Side^{2}  Perimeter = 4 × side 
Rectangle  Area = Length × Width  Perimeter = 2 (Length + Width) 
Important Notes
Here are a few important notes that should be remembered while studying 2D shapes.
 Every 2D shape can be measured by its width and length.
 All the 2D shapes are completely flat.
 A polygon is said to be a regular polygon only if all the sides and internal angles measure the same. It is irregular if all the sides are of unequal length and all its angles are of unequal measures.
Related Topics
Check out these interesting articles related to 2D shapes.
Solved Examples

Example 1: Does a rectangle come under the category of 2D shapes? The length of a rectangle is 32 m and the width is 20 m. Find the perimeter of this rectangle.
Solution: Yes, a rectangle comes under the category of 2D shapes. The length of the given rectangle = 32 m; width = 20 m
We know that the perimeter of a rectangle = 2 (length + width)
P = 2 (32 + 20) = 2 (52) = 2 × 52 = 104 m
Therefore, the perimeter of the rectangle is 104 m. 
Example 2: Does a circle come under 2D shapes? Find the area of a circle whose radius is 6 cm.
Solution: Yes, a circle comes under the category of 2D shapes. The area of a circle = π × r^{2}; where 'r' is the radius of the circle and π is a constant whose value is 22/7 or 3.14.Area of the circle = π × r^{2}
= 3.14 × 6^{2}
= 3.14 × 36
= 113.04 square cm

Example 3: Identify the 2D shapes from the following. Circle, rectangular box, Rubik's cube, hexagon
Solution:
Among the given shapes, a circle and a hexagon are 2D shapes because they do not have any thickness or depth. A rectangular box and a Rubik's cube are 3D shapes because they have 3 dimensions, (length, width, and height).
FAQs on 2D Shapes
What are 2D Shapes?
A 2D (twodimensional) shape can be defined as a plane figure that can be drawn on a flat surface. It has only two dimensions – length and width, with no thickness or depth. Some of the basic 2D shapes are rectangle, pentagon, quadrilateral, circle, triangle, square, octagon, and hexagon.
What are 2D Shapes and 3D Shapes?
A flat shape that has two dimensions length and width, is a 2D shape, whereas, a shape that has three dimensions  length, width, and depth (height) is a 3D shape.
What are the Properties of 2D Shapes?
A 2D shape is a flat shape that can be drawn on a plane surface. As the name suggests, it has only two dimensions of length and width without any thickness. While some 2D shapes have sides and vertices, others are made up of curved lines.
How many 2D Shapes are there?
There are many different kinds of 2D shapes, like the rectangle, pentagon, quadrilateral, circle, triangle, square, octagon and hexagon. These are flat shapes that can be drawn on a flat surface.
How to find the Area of 2D Shapes?
The area of a 2D shape is the space occupied by it. Since there are different kinds of 2D shapes like circle, square, rectangle, etc., there are different formulas used to find their areas. For example, the area of a circle can be calculated with the help of the formula, Area = πr^{2}, where 'r' is the radius of the circle and π is a constant with a value of 22/7. The area of a square is calculated with the formula, Area = side × side. The area of 2D shapes is expressed in square units.
How to Teach 2D Shapes?
Teaching 2D shapes is easy if the concept is introduced in the early years. First of all, the names of the basic shapes can be made to learn. Then, the students should be asked to identify the names of the shapes. Another interesting way can be by asking them to spot the shapes around them.
Name the 2D Shapes around the House?
Some commonly seen 2d shapes that can be seen in the house are, the rectangular surface of a notebook (rectangle), the circular shape of a clock (circle), the circular shape of a pizza, a squareshaped window (square)
Is Circle a 2D Shape?
Yes, a circle is a 2D shape because it exists on a plane with no depth. It is a curved shape that has no corners or edges.
Which 2D Shape has 4 Sides?
A quadrilateral is a 2D shape that has four sides. For example, quadrilaterals like squares and rectangles are 2D shapes with 4 sides.
Is Oval 2D or 3D Shape?
Oval is a 2D shape because it exists on a plane and has no depth. It is a curved figure with no edges or corners.