Pi Day is celebrated on March 14th (3.14 in the American calendar) around the world.
Pi (Greek letter π) is the symbol used in mathematics to represent a constant – the ratio of the circumference of a circle to its diameter – which is approximately 3.14159.
The diameter of a circle is the distance from edge to edge, measuring straight through the centre. The circumference of a circle is the distance around.
Devised by Ancient Greek mathematician and general polymath Archimedes (287-212 BC), pi is an irrational number, meaning it continues infinitely without repetition or pattern.