Plane Shapes
A shape can be defined as the boundary or outline of an object. A plane shape is a twodimensional closed figure that has no thickness. A plane in geometry is a flat surface that extends into infinity in all directions. It has infinite width and length, zero thickness, and zero curvature. It is actually difficult to imagine a plane in real life, there is nothing that we can use as a real example of a geometric plane. We can see an example of a plane in coordinate geometry where the position of any given point on a plane is defined with the help of an ordered pair of numbers, or coordinates. Coordinates show the correct location of points in the plane. Let us learn about plane shapes in detail.
What are Open and Closed Shapes?
A closed figure can be made of straight or curved lines. It has no opening whereas an open figure is made of either straight or curved lines. However, it has at least one opening. Example of closed and open shapes are shown in the image below.
Sides and Corners of Shapes
We have learned what plane shapes are and what they look like. Plane shapes are twodimensional, e.g., squares, triangles, and circles. The straight lines that make up a plane shape are called sides. The points where two sides meet are called corners.
What are the Different 2D Shapes?
Observe a sheet of paper. You can see how long and how wide it is. These are the two dimensions known as length and width. A twodimensional shape does not have any depth. 2D shapes are closed shapes that are created by joining straight/curved lines together.
The common 2D shapes are:
Shape Name  Number of Sides  Number of Corners  Property 
4  4  A square is a quadrilateral with four equal sides and four right angles.  
4  4  A rectangle is a quadrilateral with two pairs of equal and parallel opposite sides and four right angles.  
0  0  A circle is formed by the set of points that are at a constant or fixed distance (radius) from a fixed point (center) in the plane.  
3  3  A triangle is a closed figure or shape with 3 sides, 3 angles, and 3 vertices.  
Polygon 
3 and more than 3 sides  3 or more than 3 corners  A polygon is a closed twodimensional figure with three or more straight lines. 
0  0  Oval has no straight line, or corner, or side to it. It is a closed shape made of curved lines. 
Let us learn about polygons.
What are Polygons?
In geometry, a polygon is a closed twodimensional figure with three or more straight lines. The Greek word ‘Polygon’ consists of Poly meaning ‘many’ and gon meaning ‘angle.’ We see many different polygons around us. For example, Have you ever seen a honeycomb? Can you guess ideally, how many sides a honeycomb could have? A honeycomb is hexagonal in shape. You can very well relate the shape of a 6sided polygon with a honeycomb.
The types of polygons are categorized into three major forms:
Look at a few different types of polygons shown in the below image.
Important Notes
 Quadrilaterals are foursided closed figures made of straight lines.
 Polygons are closed geometric shapes made of straight lines. They are named after the number of sides they have.
Related Topics on Plane Shapes
Solved Examples on Plane Shapes

Example 1. Help Ruth figure out how many sides are there in the given shape. Is it a closed or an open shape?
Solution.
Count the number of straight lines in the star. There are 10 straight lines.
We can trace the outline of this star without any break. Hence, it is a closed shape.
It is a closed shape with 10 sides and 10 corners. 
Example 2. Anna needs help in picking the only hexagon polygons.
A hexagon has 6 sides.
So Anna should pick the polygon with only 6 sides.
The 6sided polygons are:
Now Anna has picked all the hexagon polygons. 
Example 3. Help Ruth figure out the polygon shape in the hanger
Solution: The hanger looks like a trigon or a threesided polygon because it has three sides. It is also called a triangle.
FAQs on Plane Shapes
Is a Circle a Polygon?
A polygon is a closed shape formed by straight lines. A circle is a round shape formed by curved lines. Therefore, a circle is not a polygon.
What is the Difference Between 2D and 3D Shapes?
A 2D shape has two dimensions whereas a 3D shape has three dimensions  length, width, and height.
When Depth is Added to a 2D Shape it Becomes?
When depth is added to a 2D shape with length and width, it becomes a 3D shape.
How Many Triangles are There in a Pentagon?
The number of triangles is 35 in a pentagon when all diagonals are formed.
What are the Different Plane Shapes?
The basic plane shapes are triangle, square, rectangle, oval, circle, and polygons.
What is the Shape of a Protractor?
The protractor is in the shape of a semicircle with markings of angles from 0° to 180 on it. There is one more type of protractor with which we can measure complete 360degree angles. It is known as a 360degree protractor and is round in shape.
Is a Sphere Solid or Plane Shape?
A sphere is a solid shape defined in a 3dimensional space. It has no edges or vertices (corners).