PI is among the significant constants of mathematics and equivalent to 3.14159 (approx). In Euclidean geometry PI represents as a ratio of the circumference of a circle to its breadth which is equal to the ratio of the area of a circle to the square of the radius of a circle. PI is used in many formulae in science, mathematics and also used in engineering. PI cannot be shown as a fraction m/n, (m and n are integers) because it is an irrational number. Accordingly its decimal representation neither ends nor repeated.
Apart from being irrational, Pi is transcendental number that means it has no fixed series of the algebraic operations on the integers which could ever create it. If we will look at the record of mathematics, hundred times attempt has been made to actually find out Pi more correctly and to understand its nature; concern with the number at large has carried over in to culture. In Greek words the name of this letter is pronounced as PI and in English it is pronounced as Pie.
PI is used in the formula as it helps in finding the circumference or the perimeter of a circle. To remember a long number of digits became a mania for some people this took place even before computers were able to calculate PI. In the 20th century when advance digital computers came in to the existence increased the rate of new PI calculation series.
Actually the value of PI has been shortened to 50 decimal places but originally its value consists of more than trillion numbers. But basic applications such as to find the circumference or perimeter of a circle will hardly require more than a couple decimal places. For instance the value of PI shortened to 11 places of decimal is more than enough to calculate the perimeter or circumference of the globe with exactness of a millimeter and also one shortened to 39 decimal places is enough to find the circumference of a circle that can be fit in the universe to a precision equivalent to the size of a atom like hydrogen atom.