pi

pi is a number. The number is 3.1415926535... (to 10 decimal places).

It is called an irrational number as it cannot be expressed as a fraction.

The decimal places go on forever, and do not have any pattern.

The number has been names pi (a letter of the Greek alphabet) and has the symbol;

It is used a lot in Mathematics, but at the level you are studying, mainly to help calculate the area and circumference of a circle.