The objects around us come in various shapes and sizes. In general, we can see shapes such as triangles, squares, and circles everywhere around us. Moreover, shapes such as a sheet of paper, have only length and breadth. Thus such shapes are 2D or two-dimensional. While other shapes such as the shape of a house, have length, breadth, and height. Thus such shapes are 3D or three-dimensional. Let’s learn more about 2D and 3D shapes!

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## 2D Shapes

In geometry, a shape or a figure that has a length and a breadth is a 2D shape. In other words, a plane object that has only length and breadth is 2 dimensional. Straight or curved lines make up the sides of this shape. Also, these figures can have any number of sides. In general, plane figures made of lines are known as polygons. For example, triangle and square are polygons.

### Examples of 2D shapes

Rectangle, circle, square, triangle, quadrilateral and pentagon are some examples of 2D shapes.

## 3D Shapes

In our day to day life, we see several objects around us which have different shapes. For example, books, ball, ice-cream cone etc. One thing common in these objects is that they all have some length, breadth and height or depth. Thus they have three dimensions and so are known as 3D shapes. The D in 3D stands for dimensional. 3D shapes occupy space. In a world with three dimensions, you can travel forward, backward, right, left, and even up and down.

### Examples of 3D Shapes

Cuboid, cube, cylinder, sphere, pyramid and cone are a few examples of 3D shapes

*Understand the concept of Polyhedron here in detail.*

## Faces, Edges, and Vertices

The object below is a cube.

The corners of the cube are its vertices. The 12 line segments that form the skeleton of the cube are its edges. The 6 flat square surfaces that are the skin of the cube are its faces. Observe that the two-dimensional figures can be identified as the faces of the three-dimensional shapes. For example, a cylinder has two faces which are circles. Also, a pyramid has the triangle on its faces.

## Nets for building 3-D shape

A net is a two-dimensional representation of a three-dimensional figure that is unfolded along its edges. It represents each face of the figure in two dimensions. In other words, a net is a pattern made when the surface of a three-dimensional figure is laid out. Thus showing each face of the figure. A solid may have different nets.

For example, a box is solid. It’s a 3D object with the shape of a cuboid. Below is a net pattern for a box. Copy an enlarged version of the net and try to make the box by folding and glueing the faces together. You may use suitable units.

Furthermore, different shapes have different nets.

## Polyhedron

A solid shape bound by polygons forms a polyhedron. The word polyhedral is the plural of word polyhedron.

**Faces:**Polygons forming a polyhedron are its faces.**Edges:**Line segments common to intersecting faces of a polyhedron are its edges.**Vertices:**Points of intersection of edges of a polyhedron are its vertices.

In a polyhedron, three or more edges meet at a point to form a vertex. Some examples of polyhedrons are cuboid, cube, pyramid, and triangular pyramid.

## Prism

A prism is a solid, whose side faces are parallelograms and whose bases are congruent parallel rectilinear figures.

## Solved Examples For You

**Question 1: **Which of the following is true for a polyhedron?

- Polyhedrons are 3D figures.
- They always have a closed surface.
- A line joining any two points on the surface always lies in inside the shape.
- Both bases are parallel to each other.

**Answer :** (i) and (ii) are true.

**Question 2: **What are 2D shapes?

**Answer:** 2D shapes refer to all those shapes that we can lay on a flat piece of paper or any mathematical plane. The most common example of 2D shapes is the drawing of squares, triangles, and circles that you make in childhood. Besides, 2D shapes exist all around the world.

**Question 3: **How many 2D shapes are there. List some of them.

**Answer:** Some of the most common 2D shapes are triangle, square, rectangle, polygon, pentagon, hexagon, heptagon, octagon, nonagon, decagon, etc. However, there are countless shapes that go on from triangle to n-gon where n represents the number of sides.

**Question 4: **What are the properties of 2D shapes? ** **

**Answer:** There are no fixed properties of the 2D shape. As each shape have a different number of sides and for each shape, properties vary. But, every 2D shape is flat and is enclosed.

**Question 5: **Can 2D shapes be held?

**Answer:** No, we cannot hold 2D shapes because they appear on a piece of paper or card that the 2D shapes are drawn on. Although you cant’ hold 2D shapes themselves. Besides, these flat are not flat because if you make a pile of them, then they have height and you can hold them.

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