Kate Bush sang over 100 digits about this symbol, the ratio of the circumference of a circle to its diameter
This polygonal algorithm dominated for over 1,000 years, and as a result  is
... [DOC] [TLE] pi.doc - The Institute of Mathematical Sciences [PAR] It is the ratio of the circumference of a circle to its diameter, d: C = pi d = 2 pi r, 
where r is the radius.