letter of the Greek alphabet (Π, π)
the symbol (π) designating
the ratio of the circumference of a circle to its diameter
the ratio itself, equal to 3.14159265+: often approximated as 22⁄7
Webster’s New World College Dictionary, 4th Edition. Copyright © 2010 by
Houghton Mifflin Harcourt. All rights reserved.
Word origin of 'pi'Gr pi, earlier pei < Sem, as in Heb pē