The number π is a mathematical constant, approximately equal to 3.14159. It is the ratio of a circle‘s circumference to its diameter. It is also called Archimedes’ constant because the Greek mathematician Archimedes is credited with the first theoretical calculation of π. Pi is the crucial constant in any equation that involves circular or harmonic motion. It’s one of the important relationships in mathematics.
The fundamental constant of physics, the Boltzmann constant, is one of the seven "defining constants" that have been given exact definitions.