The discovery of pi (π) as a mathematical concept has a long history involving multiple civilizations and mathematicians. The earliest use of pi dates back about 4,000 years to Babylon and Egypt, where it was applied approximately in construction. However, an accurate mathematical understanding and calculation of pi began with the Greek mathematician Archimedes around 250 B.C.E. Archimedes devised the first algorithm to approximate pi by inscribing and circumscribing polygons within a circle, progressively refining his estimate to about 3.14. His work marked the first rigorous and systematic attempt to calculate pi's value using geometry. Later, in 1706, the Welsh mathematician William Jones was the first to introduce the Greek letter π as the symbol to represent this ratio, bringing clarity and practical use to the concept. Pi's infinite decimal nature has since been explored and expanded by many other mathematicians and through modern computing. Thus, while pi as a concept was known to ancient civilizations, Archimedes is credited with the first precise mathematical calculation of pi, and William Jones introduced the now-standard symbol π for it, both contributing critically to our modern understanding of pi.