A 2D (two-dimensional) 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 two dimensional 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 (three-dimensional) shape has three dimensions – length, width, and height. For example, a dice is three-dimensional 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.||Types of 2D Shapes|
|4.||Area and Perimeter of 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 2D shape made up of straight-line segments which are connected with each other, thus giving it a closed shape. A circle, square, rectangle, and triangle are some examples of two-dimensional 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.
Types 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.
A circle is a closed 2D shape made up of a curved line with no corners or edges. Some real-life examples of the circle are coins, wheels, and pizzas. A circle consists of various parts like the radius, diameter, circumference, and so on:
- 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.
A triangle is a 2D shape with three sides and three vertices (corners). It is a polygon whose interior angles add up to 180°. Some real-life examples of a triangle are traffic signs, pyramids, and nachos. The following figure shows the sides and vertices of a triangle.
A square is a 2D shape with four equal sides and each angle is equal to 90˚. Some of the real-life examples of a square are: a loaf of bread and a chessboard.
Observe the given square PQRS and note the following properties:
- 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 ̊.
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 real-life examples of a rectangle are table tops, blackboard, cardboard, etc.
Observe the given rectangle ABCD and note the following properties:
- Side AB = DC
- Side AD = BC
- Side AB is parallel to DC.
- Side AD is parallel to BC.
- All four angles measure 90 ̊.
Pentagon is a 2D closed polygon with five sides and five interior angles. Some of the real-life examples of a pentagon are the black sections on soccer balls, school crossing signs, the Pentagon building in the US, etc.
Observe the given regular pentagon and note the following properties:
- All five sides are equal in length.
- Each interior angle measures 108°.
- Each exterior angle measures 72°.
A hexagon can be defined as a 2D polygon with six sides, six vertices and six angles. Some of the real-life examples of a hexagon are the honeycomb cells and metal nuts.
Observe the given regular hexagon and note the following properties:
- 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 × r2 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 = Side2||Perimeter = 4 × side|
|Rectangle||Area = Length × Width||Perimeter = 2 (Length + Width)|
Difference Between 2D Shapes and 3D Shapes
The following table shows a comparison between 2D and 3D shapes.
|2D Shapes||3D Shapes|
|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||x-axis and y-axis||x-axis, y-axis and z-axis|
|Examples||Rectangle, square, circle, triangle, etc.||Cylinder, sphere, cube, prism, etc.|
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.
Check out these interesting articles related to 2D shapes.
Example 1: The length of a rectangle is 32 m and the width is 20 m. Find its perimeter.
Solution: length = 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: Find the area of a circle whose radius is 6 cm.
Area of the circle = π × r2
= 3.14 × 62
= 3.14 × 36
= 113.04 sq. cm
Example 3: Calculate the perimeter of a regular hexagon whose one side is 15 units.
All the sides of a regular hexagon are equal; and one side = 15 units.
So, the perimeter of the hexagon = number of sides × length of one side
Therefore, perimeter = 6 × 15 = 90 units.
FAQs on 2D Shapes
What Are 2D Shapes?
A 2D (two-dimensional) shape can be defined as a plane figure that can be drawn on a flat (or plane) 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.
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.
What Is a 7 Sided Shape?
A 7-sided shape is called a heptagon. It has seven sides, seven vertices, and seven interior angles.
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.
How Do 2D Shapes Differ From 3D Objects?
A flat shape that has two dimensions - length and width is a 2D shape, whereas, a shape that occupies space and has three dimensions - length, width, and depth (height) is a 3D shape.
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.