Pi (Π) - GCSE Maths Definition

The lowercase letter pi, 𝜋, is used to represent a mathematical constant that is the ratio between any circle's diameter and circumference. 𝜋 is an irrational number, meaning that it has no end, or repetition of, its decimal places. The first few digits of 𝜋 are 3.141 59.... 𝜋 is frequently rounded, and used, rounded to three significant figures which is 3.14.

In GCSE Mathematics, 𝜋 is used in solving problems relating parts of a circle to each other, such as radius, diameter, circumference, arc length, area, sector area. Sometimes you may be required to give an answer 'in terms of 𝜋', meaning a final answer may be something like '4𝜋 - 3'. You should know how to access the 𝜋 button on your calculator, and use it to find answers that require rounding - for example, '4𝜋 - 3 = 9.566 370 ... = 9.57 (2 decimal places)'. Some modern calculators may leave answers 'in terms of 𝜋' in simple calculations.