There is a common misconception among people that Pi is just a quirky concept that is interesting only for scientist and mathematician. This taught arose as we commonly see usage of Pi in geometry, trigonometry, complex numbers and many other concepts. Reality is that there is lot of science involved behind the making of Pi. And March 14^{th} is celebrated as Pi day all over the world because the value of Pi is 3.1415. As decoded from the value 14 march was declared as world Pi day. And with extension of the value 3.1415 the 2015 Pi day was considered to be a special celebration day as march 14^{th} with year 2015 i.e. 3.14.15 comes once in 100 years.

**History of Pi**

In ancient civilization, circle was the first shapes noticed. They believed that we are living in a world which is round and also discovered that all planets, sun and moon also was circular in shape. So according to ancient Greeks circle means a sense of balance in nature. Scientists wanted to find out the area of these circular objects. But finding the circumference of bigger circles was a challenge to scientists. That is when mathematicians discovered that ratio between diameter and the circumference of circle was a constant. This ratio remained unchanged, for every circle irrespective of their sizes. Finally mathematicians conclude the constant value as 22/7 which is 3.14.

**Pi Symbol**

Pi is represented by π the 13^{th} letter of Greek alphabets. The symbol for pi was assigned in the 18^{th} century even though the value was discovered like 4000 years ago. It was William Jones, a mathematician who began the use of symbol π for the ratio of circumference and diameter. Leonard Euler, a Swiss mathematician used this π in all his theories and that is when π was bought into popularity. Later they also discovered that the value of Pi is a non terminating decimal and irrational number. The ratio of circumference and diameter is an infinite number i.e. decimal digit has infinite number of integers.

100 digits of pi are 3.141592653589793238468327950288419716939937510582097494459230781640628620899862803482534825342117067

Luckily we don’t have to remember all these 100 or 1000 integers of the pi value. It is no less than impossible. For simplicity the scientists have declared the pi value as 3.1415 or rounding off the third and fourth integer it was declared to use π=3.142

**Significance of π**

Pi is used in almost all the science and math concepts be it construction of buildings, calculation of size of celestial bodies, trigonometry, statistics, physics and so on. To learn circle and its properties means you must compulsorily learn about pi, this is how we learnt in school too. People learning about universe or irrational numbers know how important it is to learn about Pi. Most of the scientific calculation use Pi with digits upto 1000 and more for reaching the accuracy.

Definition of Pi is beyond numbers. Students define the value of Pi as 3.142, scientists define as 3.1415………… until the number of digits they need for their purpose and engineers define as 3 or 4.