<center>''See also [[Talk:Pi#Pi_contains_pi|Pi contains pi]]''.</center>
'''Pi''', or '''[[Archimedes]]' constant''', is perhaps the most important number in all of [[mathematics]] and engineering. It is defined as the [[ratio]] of the [[circumference]] of a [[circle]] to its [[diameter]], and represented by the Greek letter '''<big><math>\pi</math></big>'''. It was first used with its current meaning in 1706 by a [[Welsh]] mathematician, William Jones,<ref name="hist">{{cite web
| url = http://www-groups.dcs.st-and.ac.uk/history/HistTopics/Pi_through_the_ages.html