**Introduction of Pi (π)**

Pi (π) is a mathematical constant that is the ratio of a circle's circumference to its diameter, and is approximately equal to 3.14159. It has been represented by the Greek letter "π" since the mid-18th century, though it is also sometimes written as pi. π is an irrational number, which means that it cannot be expressed exactly as a ratio of two integers (such as 22/7 or other fractions that are commonly used to approximate π).

**Definition**

The circumference is slightly three times longer than the diameter. This ratio is usually called pi (π).

π is commonly defined as the ratio of a circle's circumference (C) to its diameter (d). Hence, π = C/d. The ratio of C is to d is always π:1, regardless of the size of the circle.

**Name**

The symbol used by mathematicians to represent the ratio of a circle's circumference to its diameter is the Greek letter π. That letter (and therefore the number π itself) can be denoted by the Latin word pi. In English, π is pronounced as "pie". The lower-case letter π is not to be confused with the capital letter Π, which denotes a product of a sequence.

**Properties**

The number π is a mathematical constant that is the ratio of a circle's circumference to its diameter. The constant, sometimes written pi is approximately equal to 3.14. It has been represented by the Greek letter "π" since the mid-18th century. π is an irrational number, meaning that it cannot be written as the ratio of two integers, such as 22/7 or other fractions that are commonly used to approximate π. π goes on forever and can’t be calculated to perfect precision; 3.1415926535897932384….. The numbers do not repeat periodically but seems to pop up randomly. π is a transcendental number, a number that cannot be expressed in any infinite series or algebraic operations.