What is a circle? It is not some thing which invented like a place or an object. It is a symbolic representation of a figure that was invented for the alphabets and numbers. When we look at the wheels, the Sun, the Moon, pulleys, gears, ball bearings, are all circular in shape. Of course the shape of our Earth is spherical. Its cross section is a circle. Apart from this, if we study about the microbiology, the lens used here is circular. You might be aware of Ferry's wheel, which rotates about the fixed axle. We can easily identify the different parts of a circle from this. In this section let us study about the different parts of a circle.